I don't know about his reason, but I have cleaned many a ball python right after I pull the male from breeding her, the females will "evacuate" in the tub(if she has been eating) before she allows him to do his thing
It's a nasty thing when one or both of them move about and spread the yuk all over.
Or sometimes their poo is a bit runny and they spill their water bowl and it turns the whole tub and it's contents a nice chocolatey brown color![]()