What happened to the French blockade of the Dutch ships?
Looking back on that update, I can see I didn't spend much time explaining that - I'm not sure why, as I had some notes to that effect. Sometimes I don't get everything into an update which I'd planned to.
Sabran doesn't have a lot of ships - three frigates, a handful of corvettes, and the rather unimpressive Genoese feluccas - and he can't devote them all to San Fiorenzo, because Bastia and the coast of Aleria are still rife with smugglers. His frigates are also quite small; his flagship, the Flore, is a 26-gun frégate légère ("light frigate"), a mere Sixth Rate by British standards, of an old-fashioned demi-battery design. It's really more a large corvette than a frigate, and doesn't have the cruising ability of the "true" frigates of the later 18th century. The galleys, meanwhile, are practically useless for long-term blockading because of their demands for water and provisions. The result is that Sabran has only a few small ships with rather mediocre cruising times which have other urgent duties, while Keelmann just sits in one place for weeks as he negotiates with Theodore, waits for his cargo to arrive, and then waits for the best possible weather to escape.
Initially, Sabran hoped that he could simply pounce on the "armada" as it exited the bay, but as days turned into weeks maintaining a consistently strong blockade with so few ships became impossible. Keelmann, meanwhile, could wait for the perfect moment to escape, when the winds seemed most favorable to him and least favorable to the French. As a consequence, owing to good winds and a reduced blockading force, the "armada" was able to slip through at an opportune moment.
IOTL, the French and Genoese had a hard time with smugglers, and were most effective at catching them when they were unloading their cargo and thus stationary and vulnerable. ITTL, the Corsicans were able (until Boissieux's summer campaign) to control several fortified ports like Bastia, San Fiorenzo, and Isola Rossa, which meant that the French and Genoese could not just pounce on unloading ships in these ports lest they be blown away by the coastal batteries. With their limited naval forces, this makes interdiction tricky for the French and Genoese.