I really don't understand people getting offended over "You don't look trans"

So for example, imagine you're a trans person and someone finds out you're trans and they say "Woah you don't look trans" as a compliment. For some reason I've noticed some people get extremely offended by that phrase and personally I don't understand it (of course I'm not trying to downplay anyones feelings as they have their reasons as to why they are offended, but still I don't understand). To me the whole point of being trans is that I do not want to look trans, I want to look like a man, or in the case of trans women they want to look like women.

I've heard some people say the reason they're offended is because the phrase implies that looking trans is a bad thing, but I really don't see how it implies that, cause it just sounds like the person is complimenting you on how you pass as your gender well and not that looking trans is bad. And even more surprisingly a lot of the people (though obviously not all) who I've seen get offended by that phrase are not trans and are getting offended on behalf of trans people. Of course its not going to be the same for everyone, so what are your thoughts?