I'll agree that snakes don't particular care for human interaction, and that it's more of a relationship based solely on tolerance, but after your eloquently worded assertions, I still don't see the harm in this!
I want a snake that can be handled by anyone, and that is adjusted to being handled in a variety of ways. If we can coax our animals into letting us hold them period, surely acclimating them to regularly having their vents inspected is no more stress inducing than the prior.
I'll admit complete ignorance to snake anatomy, but I do know that coaxing a bowl movement via warm water soak is in no way comparable to an actual laxative. True laxatives work in various ways to empty the intestines. Yes, emptying the intestines too quickly can disrupt absorption of nutrients and reabsorption of water. Using an exterior method to entice a bowl movement is not at all inducing peristalsis of the intestines, nor is it providing any lubrication to the intestinal wall. All soaking does, really, is somehow relax the snake to the point that it can defecate. The stool has already been formed, nutrients have already been absorbed, water has already been retained.
If you soak a snake when it doesn't have to poop, I'm willing to bet my life's savings ($23.45) that it's not going to do sh*t (pun fully intended)
Of course, I have absolutely no credentials under my belt and am not claiming expertise in any area