In the interest of being fair, I think we're all jumping on the surgeon here. You have to remember that the surgeon has not been made aware that the individual is trans.
To compare it, this is like a woman and a man walking into a salon and both asking for a short hair cut. With the man, there's no big deal made of it, it's just clip away to whatever style he wants, no worries. He's not going to freak about having short hair, he's a man! The woman however, she's going to be questioned to make sure. And then the hair dresser is going to cut it back a bit, and if they're a decent hair dresser, they'll probably not make it as short as they've been given allowance for. They'll cut it a bit longer than requested and ask again and only go shorter if the woman says to go shorter. She's a woman, and she could very well freak if she ends up with too short hair, or it looks too manly.
This is exactly the situation the surgeon is in right now! Someone might say "I want really small!" and this is purely because they've had to deal with far too big for too long that they get overexcited about losing that and figure they want them really small. It's like a short person being offered some kinda surgery to make them taller. 5'8" would be more than enough, but they're going to want taller because they're so used to being short. But if they were to be too tall, everything else would be out of proportion and look wrong. The surgeon will know that a size B is actually pretty standard and fairly small. He won't want to go smaller because, well, a woman could well freak out if she comes too and there's hardly anything left! He's viewing you like that woman wanting the short haircut, or the short guy wanting to be disproportionately taller.
It really is pretty much the same except worse, hair grows back - boobs don't! So the surgeon is probably not wanting to go too small or trying to talk you out of it purely for what he sees as your benefit right now, because he just sees you as another female client. I would actually strongly suggest you tell him. If he's not accepting, you find another surgeon. If you tell him, then he's not going to worry about you freaking out about them being too small, and he may even go further than an A and you'll be one of the lucky folks to get the whole thing there and then!
