Yeah, this bothers me. I would've honestly preferred them to just leave the coaches as is until next year's game (I'm pretty sure that's how all games have operated up to this point).
I just started a batch of new Dynasties with BYU, Vanderbilt, Illinois, and Duke and this is bothering me so much; especially since they also (seemingly) took out the ability to rename and customize the generic fake coaches and still be able to retire while the name and other changes remain.
I really don't understand WHY they actively make their game worse for the players with this now removing real coaches in the middle of the CFB Playoffs and the update before that removed being able to Encourage Transfers before the offseason Transfer Portal recruiting opened up. Both of those things have made my enjoyment of the game suffer dramatically (I know to some that sounds dumb but more options is always a good thing, even if you, yourself, don't use them).