>According to whom? Doesn’t seem out of the question for people to both have viewed them as demons or monsters and for certain people to have mated with them

cf. The Gnarly Man[0][1] by L. Sprague de Camp. It's fiction, but addresses that facet of potential interactions between hominid species.

[0] https://en.wikipedia.org/wiki/The_Gnarly_Man

[1] https://www.galacticjourney.org/stories/600411gnarly.htm