I suppose it's because in my mind there isn't a clear distinction between the time before Ishma'il I and after.
You are right in that obviously in real life one doesn't "form Persia" like in the game
Before Ismail there was arguably no Persian nation though (the sect most of the time controlled some land in Tabaristan, often less than one game province), and the Safawiyya were around almost 100 years before Ismail. The sect was the vehicle used to create a Persian nation by Ismail and his followers and allowed them to fight off all the different states currently in the land when he became it's leader. I still think that means that forming the sect after you've unified Persia makes little sense. In fact had such a sect arisen after the Safavid takeover it would likely have been struck down as fast as possible. The Safavids did not like deviants in general and disliked Sufi sects in particular (even though they themselves started out as one).
Some Safawiyya related decision would make more sense for the Ak Koyunlu as those were responsible for the initial aquisition of real political power for the sect (realistically it'd come back to bite them though as their sponsoring of them meant that they were kicked out of Persia by the Safawiyya later on
).
