This is fair! I'm pretty sure some part of my brain is rejecting the term "reverse harem" and wishing there was an entirely different name for the concept (maybe something to do with insects? I know that bee hives, for example, have one female mating with multiple males), and is trying to come up with funny ideas to expand on it in self-defense. And also as a mental rejection of what I'm pretty sure the actual terms will end up being, of "Lesbian Harem" and "Gay Harem". (If the culture goes that route, I'd much prefer Sapphic and Achillean harems, but, well, we already acknowledged that it's not actually up to me 😛) I guess Diamoric Harem could work for any nonbinary/agender/etc characters who don't feel like the others could work.

I like Pan Harem, but I feel like it should be slightly expanded to Pansexual Harem of Panromantic Harem, to specify that the main character is not part of every harem in existence.

Inverse Harem might also describe one of those older fanservice titles, where there's one guy who goes gaga over everyone even remotely female but they are (almost?) all abjectly uninterested in him (such as Lum! Urusei Yatsura, or if Pokémon were about Brock and ever had more than one regular female castmate at a time).

I like Null Harem for an oblivious ace and/or aro character surrounded by love interests! And Sideways Harem could also definitely work for at least one of those. ...More likely ace, I'm thinking, given a certain amount of hentai titles.