"Tags" are a big source of tragic anguish on this site. People are constantly arguing about what the exact meaning should be.
In some cases, that's due to social misconceptions that go beyond this site or even porn in general.
In some cases, it's because people who really REALLY REALLY hate a given concept with declare that anything which even touches on it counts, like "the peas touched my mashed potatoes, so I threw out my entire plate of food."
In some cases, it's because the definition is seriously broad enough that within that scope, different people have different preferences.
Harem: starting from the real life word, it's not even about sex. It's a wealthy man who takes multiple women, especially female relatives, into his care, provides for them, protects them, and eventually arranges marriages for them. At the other end of the spectrum in porn, some people feel it must be a 100% one-sided poly-amorous collection of sex partners where the harem master may have as many partners as possible but each of them must never be touched by another living being, or possibly masturbate. So, anything between those two extremes should technically count as "harem," but people who don't like specific other things will say it doesn't count if some other aspects spoils it for their personal preferences.
Personally, as long the relationship exists within the harem and noone is trying to "take away" one of the girls, I don't mind letting the girls have fun with each other. Seeing two women together is hot to me (or a woman with a trans woman for that matter), so why would I stop them from putting on a show? I like games where the MC actually cares about other human beings and wants them to be happy, so if the girls want to party among themselves while I'm busy elsewhere, why should I stop them?
Most games I see do not have any separation of present vs future/planned tags, but I guess that's a thing. If you want to be clear about what's currently in a game, I would definitely list future tags also as a separate list. A lot of games are slow burn or just take a few updates to get to certain specific things, and people need to be able to tell what type of game it is before those things come up, or else people will get upset when they "suddenly" appear. So, if incest relationships are a focus of the game, than obviously incest needs to be mentioned somehow even before the actual sex happens.
Welcome to being an AVN dev. NTR, harem, and "futa/trans" are likely to be the biggest argument starters from what I've seen.
