I've heard stories of dojos eating snails, it's just the 3 I have owned never do
. They have all been in a tank on my desk, so it gets a lot of watching, and it has a ton of snails, too. I never find snail shells in that tank (although I often do in tanks with botias or puffers). With all the other loaches, I hear them crunch the snails, too.
It's not most loaches that eat snails, it's most Botias. There are plenty in the loach family that don't eat snails.