The “for” part is what makes this a backhanded compliment. It heavily implies prejudice/preconceived notions, because there is no need to compare to the other group. While it might be a compliment directed at the person, it’s implicity demeaning to the community you are getting compared to. It’s not necessarily a firmly or consciously held believe, but it still shows what they are expecting.
I can see what you mean, but you still get reminded that you are trans/don’t get clocked fully as the gender you’re presenting as.