My experience has been that transgendered people will correct you politely when accidentally misgendered. They get it. They don’t like it, but they get it.

It’s the cisgendered people who get offended when they are accidentally misgendered (i.e. calling a cis-female who has masculine features “he/him”).

No different than assuming a fat woman is pregnant or a man with a high voice is gay. And the embarrassment is felt all the same, for both parties.