Does it really matter? The term 'capital' is pretty meaningless in and of itself. There are countries with multiple capitals. There are countries without a capital. It isn't always the centre of government and it doesn't even have to the biggest city in the nation.So why should it matter if it isn't officially Moscow?
Of course it doesn't matter. It's not supposed to. It's an interesting look at what might have been, just like everything else on this board.