The difference is degree of escalation. In your example it’s “I was being sexually assaulted” and in the gay panic defense it’s “I interpreted reasonable but unwanted flirtation as danger and responded with violence.” It’s generally used in situations where as a woman if I attacked a man I’d assume I’m getting arrested.

Now personally I have mixed feelings on banning the defense. It never works and so I think bar associations should condemn it in the same way they should condemn any defense by confessing. But I also do think it should come with additional punishment, not because “how dare you defend yourself like this” but because you’re confessing to it being motivated in bigotry. It’s “it was self defense I swear, what happened was [confession of it being a hate crime]”