But what is the illusion? Illusionism is about the GM misleading the players as to how the content of the fiction has been established. But in this case there is no misleading. The GM has followed the process of rolling on the table, which - ex hypothesi - is the same for both paths.It's illusionism in the sense that the encounters are the same regardless of the path (albeit, as I've said, a useful and accepted form of illusionism).
No. It depends on what the GM says or implies about the ostensible process of play compared to the actual process of play.If the GM simply decides the PCs encounter A, B, and C regardless of which path they take, we can both agree that that is clearly illusionism, right?
I honestly don't know what you mean by "illusionism". You don't seem to be using it in the sense I'm familiar with, which is the GM obscuring from the players the way in which they determine what happens next.