It does not make sense for them to generate on the surface

The issue could be resolved pretty easily by just including a config option to control the maximum height they will spawn at.

that seems like the crappy way of doing things. what about caves in high mountains or the twilight forest? looking too see if there's a ceiling is a much better option.

Checking for elevation is easier to code and it's the way that would put the least strain on the world generator. Having no stalagmites in mountains is a small price to pay!

since it only generates on top of stone the times where it will have to look up a lot of blocks are minimal. you have to do it properly. Alternatively you could start on the ceiling like stalactites and look down to find the floor as you're guaranteed to find one very close.

I wasn't saying your idea wasn't viable, I was just suggesting an easier solution.