I don't think it's criminal to be less-than-forthright about gender. You have the right to opt out at any time. Anyhow, the idea that gender is binary is completely outdated.
The crime here isn't misrepresentation - the crime, plain and simple, is statutory surprise sex.
Sex is strange. Gender is weird. Until you have someone's clothes on the floor, there's a good chance what's under them won't match what you expect. You should expect that.
Believe it or not, not everyone will fit rigidly into their assigned gender role, if they even have one. These restrictive and outdated thoughts on gender and its binary nature limit self-expression. Like someone else said, if you're wanting a blowjob and to get your dick wet, does it really matter where you're sticking it?
Sorry, but if you have a problem with having intercourse with a transwoman (who is functionally identical to a ciswoman), there is something mentally wrong with you. Its a good example of Magical Thinking. Or a transman, sorry for assuming your gender and sexual preferences in advance.
Here is a question to people like Top Bunk Wanker: would you feel hurt and betrayed if, after years of playing catch with your awesome father in the front yard, discovered that he had been catching with a bionic arm (because he lost his real one in Vietnam)? Or would you think "its indistinguishable from his real one, and we had lots of fun, so who cares?"