AFAIK it is essentially an auction and goes to the highest bidder.
Can't say that I agree with you, AW is not responsible for people's morals. In fact if they were there would be a lot of people saying that they shouldn't be allowing escorts to advertise and therefore not exist.
BB is better to be allowed to be advertised imho, then those looking for it can find it, hopefully saving a good proportion of the requests that SP's who don't offer it get, although I believe that they still get requests because they are clean and don't offer it
Not allowing it to be advertised just drives it underground and makes it harder to avoid those that openly offer it. Obviously many escorts who don't offer BB, will be doing it in their personal life, and there will be a small minority who allow BB to trusted regulars, but we can only work with the knowledge that is there.