I'm not sure where you read that, but out of a collection of 40+ snakes, I've only had actual defecation in water bowls maybe a handful of times total. Over the course of a year.

So I would throw away whatever it was you read, and get something more accurate to read. If that was wrong, what else might be wrong?

Water Dragons usually use their water as a potty, but ball pythons rarely even soak. Occasionally I find urates in there, but I usually find those in, around, and on water bowls, and all over the rest of the cage as well, it's just random chance.

I have noticed that ball pythons prefer to do their business in the bin corners, though.
Maybe they like having something to brace against.