NAH.

Your reasoning in wanting to give this role to your (biological) mother makes total sense.

Your stepmother did nothing wrong in assuming she would be taking on at least a part of that role, after making such an effort to be a parent to you for so long.

Your father seems to have genuinely tried to do right by everyone and simply misjudged things somewhat.

Whilst it is entirely your right to make decisions about your own wedding, it would probably be nice to find some kind of prominent role for your stepmother to play, if she will accept it - keeping the traditional mother of the bride stuff for your real mother is fine, but you can do that and also acknowledge the other woman who supported you and appears to have your best interests at heart. That’s just my thought though, obviously it’s your call.