its really not. they would have also had to sunk in the door to make the molding the same thickness. its more work, but not that hard with a hollow door. Probably less work than what they would have had to do to the top of the door that actually functions
I think they are talking about the “door” part on the ceiling (circled in white), not the door in the wall. It looks like they did put trim around the door (circled in blue), but threw the “door” up on the ceiling as an afterthought.