Tbh as someone who only writes m/f and f/f, I do see some "flaming gay stereotypes" but in my experience those characters come mostly from animanga, and mostly from animanga that's either explicitly yaoi or that is heavy on m/m fanservice. And sometimes that characterization is canon, or close to it.

That's where you tend to see a lot of pillowqueen, sub-exclusive, weirdly feminized male characters played for m/m ime. It's still not necessarily the limp-wristed stereotype you see in the West but it is annoying. Of course not every anime player who prefers m/m is like this, not by a long shot, but I see more people like that in anime fandoms than I do playing Dean Winchester or Tony Stark in m/m ships.