@mietze I'm gonna try to break it down, and I admit maybe I'm reading too much into things, but I feel like this has been an undercurrent issue for a long time.
Take for example, the earlier comment someone made to the tune of "I only create straight male characters; I feel so boring." (paraphrasing) - I'm sure it was a joke, except I think some people genuinely do have this issue. The ability to roleplay a spectrum in gender and sexuality well is most definitely an ingredient for being considered a good RPer, and I think sometimes people who opt to stay in their lane might feel like maybe they're somehow less talented/more restricted in their capacity to play, regardless of why they choose to stay in their lane - for purposeful reasons like "I don't think I can play this because I don't identify and don't think I can do anything but produce a sterotype." As @Quinn was saying.
And then there are the women who play gay men and guys who play lesbians explicitly for the kink, and not because they're exploring any kind of meaningful RP. Which I think can also lend to that notion of wanting to explore one lane while RL being in another; the concern that you will be perceived as one of these types of RP seekers. (I'm not saying it's a logical conclusion, but brains be irrational brains.)
I could also be off my rocker and communicating poorly.