It is silly to think that they need to have sex with each other to "function cohesively" or to care for each other lol, specially when they are just not lesbian/bi. It is a coomer fantasy the notion that all women con just turn bi for convenience or have (sexual) interest in other women, most don't, unless all your characters are bi which I guess you could do if you wanted.
About them being just "dolls for the mc to fuck/play" I dont see how they getting fucked by other girls in the "harem" is making them more "people" or "independent" or "realistic" if anything, it just shows that if they are not getting fucked one way or another then they really have nothing else going on in their lives. No ambitions, goals, hobbies, friendships, personality, nothing, all they do is sex. So that makes them more like brainless sex dolls that only think about sex, just not only for the mc but for whatever is available in their proximity.
I dont really know why make this issue a discussion of values (lol) and what not, if you like lesbian sex or have a lesbian fetish then go ahead and include it in your game. But dont make it seem like you include it for values or because it makes sense, or "empowers" the characters because really it doesn't.
A girl that has no interest in lesbian sex is not a sex doll and it doesnt make her less of a person or less of a realistic character than one that just falls in love and fucks whatever she has in front of her and needs to get fucked constantly or else she cant function or work cohesively with the group. She can be in the harem, care about the other women and consider them friends/family without having romantic feelings or sexual interest for them, she could even feel certain jelousy or a sense of competition, maybe she doesnt like/doesnt get along with a particular member, who knows. I think that makes it more interesting and makes their characters more like actual people than just the usual "Oh I fell in love with MC but I also fell in love with every single member of the harem and turned BI lol, how convenient for me, lets all have sex 24/7"
And I'm not saying that the dev should change his game, just bothered about the reasoning he is using. Just say you like lesbian so it will be in the game. Period.
If I was to ask for anything it would be to make the voyeur scenes avoidable/skippable because I just have no interest in voyeur scenes or lesbian stuff outside of threesome/foursomes,etc.