When I saw Pravus's Eranshahr playthrough video I noticed this too!
I understand why PDX went this route because really, this Eranshahr we form in 1444+ is a not a 1-to-1 copy of the previous Sasanian Empire or the Achaemenid Empire. It is a revitalized Zoroastrian Empire - you can see it making sense that they would combine the standards and colors of previous Persian Zoroastrian Empires in order to make a flag unique to their new, reforged empire. Granted, at first I was a little put off by this because a Shahbaz falcon with a purple standard background is combining different styles, colors, and symbols from different eras of Iranian history.
The Shahbaz falcon that PDX used for Eranshahr's flag can be traced to the Achaemenid Empire; it is the standard of Cyrus's and his descendants until the empire's conquest by Alexander.
In the game, they have a yellow Shahbaz in a purple field background (very similar style to Derafsh Kaviani: yellow lily in a purple field).
I can see why someone would prefer the Derafsh Kaviani and I wouldn't mind going that route either. I like both routes equally. I'm just glad they didn't do the Asiatic lion with a purple background - I've seen some mods with that variant and it looks ridiculous IMO.
en.wikipedia.org
Currently, a country called Mazandaran uses this flag, it should be changed to another flag.
