Snakes digest many different kinds of beddings and I have never seen anything happen to one of them.. unless it was a poisionous bedding like cedar buuut..
Yeah I noticed twice that my 20" BP swallowed small pieces of cypress mulch and didn't affect him at all. But now I just try to flatten the substrate as much as I can with my hand (or something else if you're afraid of a bite) when I clean the cage. No problems since!