You forget the option where he has no clue where the story is actually supposed to go, let alone finish. He has ideas for scenes, but not an entire picture, it seems. He gets stuck writing about minute details in great length, stretching it as you say, but in the end he ends up nowhere.
He has transformed the game into a linear novel, which is fine and should make it easier for him, but he still can't deliver meaningful content. His writing is good, but over the last few years he introduced several new mechanics that never do anything and aren't even being used ever again. As I said, he loses himself in ideas for scenes and features, but doesn't know where he actually wants to go. No wonder writing takes so long when you literally have to force yourself to come up with something.
Sad thing is, we are still in the prologue. Then again, are we? What is the main game supposed to be when all of this is just the introduction?