Though this throws some minor wrenches into my predictions (Albus's magic is from the witch and the witch is likely the "messenger of god") it also kinda strengthens it a bit. Namely that it means the spell she cast on herself could be the same one as she cast on Albus, because the "messenger" here mentions that the spell on Albus (which only rewinds memories) will eventually detach him after too long, at which point he himself would be floating around time.
So I feel like it could just be that the witch herself just already became detached from using it on herself, and Albus is just on his way there.
Honestly the biggest wrench is that the messenger doesn't look like the witch, but when it comes to hooded figures that doesn't mean a whole lot, lmao. But it could also just be that the witch is maintaining the spell on Albus, and the messenger is just future Albus interacting with himself.