I think GP's "porn list people" means "people who really like lists (as if lists are pornography to them)"; see meaning 3 and 4 in https://en.wiktionary.org/wiki/porn#English.
I would say the other way around though, i.e. "list porn people".
I hope they meant list porn and English isn’t their native tongue. In the sense of people who get pleasure from making lists. Porn list people would imply people who make lists of porn which doesn’t fit the context.
I would say the other way around though, i.e. "list porn people".