Which is contingent on lend-lease providing a good part of the mobility for the Soviets to exploit breakthroughs fast enough to outpace the German retreat and take advantage of those misdeployments.
No, or at any rate not until mid - late 44. If you look at the rates of advance of the Soviet forces in 42- after Bagration they are not so different to the German rates of advance in 41 ( or in WW1 or the civil war for that matter). Soviet attacks tend to be very short legged and of limited duration when there is opposition, with initial penetrations of 1-10 km on the first day. 10km is a good march distance for a horse drawn wagon per day. The Zhitomir Berdichev offensive 24 Dec 43 - 31 jan 43 advances maybe 200km over 5 weeks or about 5 km per day. The German problem is their rate of retreat for horse drawn equipment is about the same if the horses are up day 1 and if one of the 1100 or so Russian tanks involved does not machine gun the retreating horse teams.
At which point whatever they were pulling is lost.
The Soviet sources claim ( and with some corroboration from German) that in the process they destroy 2 german divisions and a further 6 inc two mobile are halved in strength. You can pick another one if you like but the main effect is the Germans being pushed back, losing control of the battlefield and being unable to recover any materiel they lose.
This is hardly surprising there are no more roads available to the Soviets than there were for the Germans going the other way. Almost all the accounts refer to germans being pushed back not encircled except at the very tactical level with the encirclements being precipitated as much by cavalry or cavalry mech groups. Trucks no doubt help in many ways but in 43 - 44 where the armies are in contact and the main heavy lift is by rail anyway how much is questionable.
Later on when the Soviets are off their own gauge rail net and dependent on the inadequate Romanian railways and having to rebuild the net to their gauge trucks become more important but by then Overlord has happened.
Now the trucks and AFVs do provide a lot of assistance but enable the breakthroughs is a stretch because there really are no deep mobile breakthroughs and many of those result in a Soviet defeat even very late in the war.
This is fantasy analysis all tries to pretend that the less successful Soviet advances post-Citadel doesn't result in the Germans suffering vastly fewer in manpower and material losses in the east. Which means that the replacement manpower, equipment, and supplies can flow west in vastly greater quantities. Just having the replacements that the Germans sent eastward in the summer of '44 go to Normandy instead results not just in German losses during that battle being covered, but the quantity of German forces in the battle actually increasing as it drags on rather then dwindling to attrition.
The issue is not rate of advance but rate of attrition. There is no reason to suppose that the attrition rate on the easter front would be very different there is a remarkably consistent death rate in the Heer between 38 and 50k per month from July 41 ( which is at the high end) until the end of the war. There are spikes in the MIA numbers in Jan and May 43 ( Stalingrad and Tunisia) and again in July August 44 with 700k MIA over the two months but coincides with Normandy, Bagration and the defection of Romania which bags large numbers of rear area forces.
One item to note is German doctrine was to immediately attack a break in and in the west at least 80% of German infantry casualties were suffered during this counterattack.
What reinforcements going east? From a peak of 195 divs on the Eastern Front in Feb 43 by July 44 there are 124 in the East and 69 in France with 27 in Italy and 23 in South with 19 in Germany. Most of those in Germany seem to have been transferred from the East over June - down from 150 that month, down from 160 the month before and from 166 from Jan 44. A month later its 130 in the East, 72 in France 29 on Italy and 2 in Germany. Ofc by then several divisions are written off in both east and west. That says nothing about the equipment or strength of the divisions but generally those in the west are stronger and better equipped because they are closer to the production in Germany and any unit moving west takes advantage of this.
Generally from start of the 42 campaign season at least Germany is unable to replace manpower losses. Only AGS can be brought up to strength for 42. And after that they lose 6th army, 5th Panzer army and the DAK in Tunisia the whole Italian army, a couple of Romanian armies and the Hungarian army. Which may not be the best in the world but they can hold the line in quiet sectors allegedly without them someone has to be in the outposts. By 43 german 65th ID is mostly ethnic Czech and destroyed at Orsogna. Then reinforced and destroyed again at Anzio. By the time of Bagration AGC is around half its nominal strength with the rifle Bn being at least 30% ethnic Russians. At Kursk the German commanders are complaining that they will be unable to attack successfully because their infantry strength is too low.
The absolute best case after Kursk, which is still before the main LL effort arrives is the Germans are pushed back in bloody fighting pretty much as OTL with mobile elements and any reserves available having to do to Italy and the Balkans to compensate for the loss of Italian garrisons. Maybe a little better off in terms of ground lost but I doubt it In terms of casualties not at all. Outnumbered 10-1 in tanks and 5 -1 in men is not a good start point for Rumyantsev especially when brilliant genius Panzer God Manstein sends his reserve off in the wrong direction.
After that well AGC talked about AGN is snug ish but battered to all hell and the southern AGs having suffered through Zitadelle, Rumyansev the Dnepr Crossings et all with the Soviets galloping forward at an earth shattering slow walking pace one wonders where the troops will be found to go west. Apart obviously from the 40 odd divisions including at least half of the Panzer and Panzer Grenadier Divisions available already sent since Mid 43 the troops manning the air defence of the Reich to stop the Allies burning cities at will and the under and over age which will be called up in late 44 early 45.
And if they are there why the hell are they not used to bring up the troops on the Atlantic Wall to full strength and equip them with at least standard calibre guns and maybe a few horse drawn carts or bicycles.
Now as you say none of this actually adds to Western Allied fighting strength per se but it does remove constraints on shipping that force around - so the 5 divisions eventually at Anzio could be landed in the first couple of days. The Force landed at Taranto may not be limited to what you can get on and off a cruiser alongside a pier but also have a cargo ship to hand the locals will gladly as it turns out unload for you. The US 1-7 Amd div land in France earlier, with the 13 or so ID that actually land during July - August. With enough Shipping and Marseilles intact and all those trucks not in russia now who knows - Al Patch may be in Bavaria before the leaves fall with 500k vengeance crazed Frenchmen a burning and lootin up the Palatinate like great great Grandaddy and his daddy and his daddy and his daddy before him.
And if the war drags on until Early August 45 its boom boom time.