Whilst I think you are correct with the origin of the ‘Saggy Pants’ coming from the american prison system I think it had more to do with the fact that they have their belts confiscated in case they used them as weapons or the like than anything else. Hard to keep ya pants up with no belt. Then later this was adopted by the rap artists and the ‘Saggaboy’ was born.I do think there are gay implications within this too but am not quite sure if that came after the fact that their pants won’t stay up.
A classic sagga wardrobe malfunction was when the lad from JLS was seen leaving a nightclub with a humongus sweaty a r s e crack which had he had his jeans pulled up no one would have known about. YUK.
I can’t imagine it is comfortable.