My friend brought this up to me a while ago as well! It’s in all the narration in rwby, it’s very coded towards men. It could easily be an oversight, but that doesn’t really excuse it. The gender neutral words for the warriors seemed to be ‘Hunters’, huntress’ and huntsmen were just getting more specific about gender. So to use only huntsmen in the latest WoR was kind of unnecessary.
I actually noticed this the first time I watched the episode.
The idea that “masculine” is neutral while “feminine” is othered is one a lot of people have trouble shaking, it’s fairly common in the queer community. They’ve shown signs of attempting to avoid that, but they slipped up here and there, as you’ve noticed.
In another context, it’s interesting that they do this mostly on the historical segments. Women and their accomplishments are pretty commonly erased from real world history as well, their contributions downplayed or outright credited it someone else. It’s what leads to some people believing women “have never contributed anything” or are bad at a given subject like science or math.