I remember having wet pants or seeing a puddle on the floor after sitting on the loo for a poop. My mother used to smack me and say I was a naughty boy for having a wee at the same time as a poop. She said I should stand for a wee and sit for a poop.

Frankly, I can't see how wee can go under the seat if he is sitting on the loo correctly with his penis pointing down.
It must go down!
My sons have all sat on and their pants have always been dry after going.