I think your later conclusion fits best. There isn't typically a role for women to play in these kinds of FVN. If the sole focus is world-building immersion, then yes. However, I believe this creator is trying to flesh out characters they've already come up with and refining the dynamics between them. Trying to answer "why aren't there any women" in terms of world-building is a huge distraction for the writer's interest.
I can't really say I've read many FVNs with good female characters either. They're usually token characters that make rare appearances like Maria from ExcA or Cynthia from TSR. These characters are a nuisance to the story because they often kill the pacing and they don't offer much to the story so it's difficult to justify them being there. I still like them, they have interesting personalities, but they could do more than just make an appearance, nag you, then disappear for awhile as the main story continues. They become bland and predictable, and it makes the reader hate them in a way.
I'd say the better female character would be Virginia from Adastra. She doesn't appear often, but when she does, it's typically about her motives, her alliances, and her position as a woman in power. Personally, I don't really love her as a character either because she comes off as nagging you or her brother, but she does have some bittersweet moments.
Most creators who make FVNs have the goal to curate a roster of characters to romantically or sexually appeal to as many people as possible to gather support for their game. As these creators are usually single in person, and often only experienced in some coding and drawing. I'd say leave it to the people that want to make good, well-flushed out female characters that fit into the environment they've curated. While it certainly doesn't do it justice, it's best for the target audience that probably both want a men-love-men furry romance AND an interesting storyline that's well-immersed. Therefore, male characters take higher priority to accomplish these two tasks.