It just goes to show what a farcical placebo "sex change" surgery is. Doctors can mutilate your plumbing until the cows come home but you're still the gender you were born.
Most likely, he didn't have anything done with his "plumbing," because the options for women transitioning to men aren't worth it.
If you met him on the street, not pregnant, and talked with him having no sense he was born a woman, in what sense would he still be the sex he was born? You can't know what the "plumbing" is, all you have is how he presents himself and interacts with you. With many FTMs, you'd never know, except maybe for their height.
We can talk about what sex you "really" are but what does that mean if you interact with the world as a different sex and no one is any the wiser?
FYI, this is why some transpeople are not thrilled with this guy's behavior and others certainly wouldn't be comfortable doing this to their bodies. It would be painful to be read as a woman in any way.