Hi all! thanks for the replies! Thought I'd give an update on this. I did end up getting a structural engineer to have a look at this (along with every other walls in the house). He said it is not load bearing, but double header and beam across the arch did puzzle him a bit, so he also consulted with his collegues, and they still said that there is no way those closet walls are load bearing.
So I'll go ahead and knock that out. Worst case scenerio, the structural engineering report carries enough insurance in case those indeed are load-bearing.
As I do renos and cutting holes elsewhere in the house, turns out every wall on this house, even the walls that are guaranteed not-load-bearing, all have a double stud header, and a beam across doorways.