I wouldn't count on current stuff in those publications being free from AI. We're seeing it in peer-reviewed paper submissions so why not in literary forums?

If you limit yourself to stuff from maybe five years ago or older, yeah it's going to be human-written and human-edited (ghostwriting still possible).

AI is much better at generating text that resembles scientific papers than it is at literary writing. Even if they're not all flagged as AI, the incidence will be much lower because they're simply bad writing. They won't make it out of the slush pile at places like GP listed.