As for banning restroom breaks altogether, there are students who are not on the record, with respect to disability services, that have serious bladder/bowel issues. Also, this can adversely affect these student's grades, as they have to purposely skip eating or dehydrate themselves hours in advance of the exam.
Personally, while I am registered at disability services, my issues are particularly severe. I have two rare immune-mediated neurological diseases affecting my peripheral nervous system.
If I hold my bladder, I literally experience something life threatening known as autonomic dysreflexia, which is just about the worst feeling in the world: https://en.wikipedia.org/wiki/Autonomic_dysreflexia
I also look completely normal, and I can walk. So, while I do not appear disabled, I am severely disabled, and I cannot hold it. I also have severe bowel issues too, but it's TMI. I am on a last resort medication for that.
My professors limit the amount of bathroom breaks (an arbitrary amount) during the exam, and sometimes it is inadequate, especially for somebody like me who gets extended testing time. So, I had to go to disability services and explain my situation (degrading) to be allowed to use the restroom as needed. I had to have another accommodations meeting over these rules.
As for a TA escorting me to the restroom and literally standing outside the stall. Yeah, it's degrading, but go ahead, be my guest.