At a kiddie pool I visited sometimes, this happened and they drained the whole thing. Maybe there is a chlorine regime that can be applied when/if this happens to a larger pool.
There are some really nasty diseases that can spread through human waste, and I would not want to come in contact with them.
And yes, I've read the instructions, and spoken to the folks who run the pool.
Mostly I think they're just there to keep the poop in long enough to get the kid out of the pool.
Are you suggesting that perhaps some people think it is all right to leave their kid in the pool with a swim diaper full of excrement?
Swim diapers are designed to simply make sure the poop and the kid are in the same general area and that it's easy to remove them from the water as a self contained unit. It will still absolutely contaminate the water in some way, there's no escaping it.