The “owner” is sometimes considered the owner but sometimes the beneficiary is considered the owner.
I know noting about 529 accounts and I am not a tax lawyer anyway.
I did open a UGMA account with my broker for the newborn daughter of some friends of mine. It was entitled
MyName, trustee(?) FBO HerName.
From which I infer that the broker considered it hers, but only I had authority to manage it for her until she reached 21 (in my state: 18 in some other states).
So if tax laws were logical and consistent (pause here for you to get over your laughter), that should apply to 529 accounts as well.