WEll, if it does loosen the bowels that much then it may be good for IBS in the same way as a water enema. Since IBS is usually caused by things staying in the colon that irritate it and which are not normally shifted by usual transit something which flushes out the colon is a good thing. At the very least it relieves the symptoms temporarily and at best it may even stop them altogether.
I'd also suggest peppermint tea to treat IBS. Though probably best to drink that rather than use it as an enema
Enemas are generally icky and messy. Plastic sheeting around the room may be advised but if he doesn't like the idea of the mess it is probably best he does not do them to you![]()