@Bret: I really hope I didn't come off cross. If you don't buy it, you don't buy it, and that's cool. Nothing says this all has to mean the same thing to all of us. But if you'll indulge me, here's the basis for my argument:
The Angel's healing moves are what he does, you know? He picks up his angel kit and goes out bravely into the world to patch up those with the misfortune to have their guts aspilled.
His sex move, however, I think is who he is. He cares about people, and lives; he has to, or he wouldn't do what he does. His Hx goes to +3 with whoever he sleeps with because he genuinely cares about his partner; he doesn't have to like him/her, but he cares enough to really understand this person. Maybe it turns out he finds something he didn't like, and he knows to stay away; still, Hx+3 means he's in better shape to do so.
The driver drives cars, and is fast, and is awesome at it. Why? Because he doesn't want to be tied down. His sex move is disadvantageous for him because despite his burning desire to not be tied down, he's been captured and made vulnerable by his partner. It's great in the moment but there's something in it that grates against his tendencies.
Anybody can take a no shit driver or healing touch, but they flesh out what the character does, not who he/she is. Changing sex moves, since they reflect the character's fundamental philosophy, essentially rewrites his entire outlook top to bottom.