That's a strawman no one is prescribing anything about the characters or the universe. We are just playing a game of averages i.e on average monos/duplos/femmes are Y than M/D/F: the game lore itself mentions that on average duplos are hornier/have a higher libido than the other genders; does that mean the game is implying that duplos are a superior/inferior gender?
The universe is clearly varied in its designs but that doesn't mean people can't connect dots and try to infer things.
I mean.. that's exactly what's happening however?
There's been a fair few posts inferring that there would be some evidence behind futas having a superior physical build compared to duplos or regular females, based on the
very small sample of characters that we've been introduced to. As you've said, humans always try to find connections, but saying that
none of the posts are inferring anything is a bit facetious.
Also I wouldn't say that duplos are A gender, they're just all of the genders at once and likely have some wild hormonal fluctuations, likely giving them that stigma. Atleast if we base it in real world biology, which is just absolute conjecture since it's a piece of fiction, the dev can do whatever he wants in regards to that.
EDIT- I'd like to clarify that when I note "gender", I am talking about biological sex, I simply used the same term as the post I was quoting.