I would suggest that this is unlikely, unless the escort offers BB as a matter of course and therefore assumes that it is required. Important to do your research. If it is truly out-of-the-blue, stop it and then get tested asap.
More common is the habit of an escort rubbing their naked genitals against your cock. They might not view this as technically BB, but its not far off. It is not something which I am comfortable, and I will move away if I think they are getting too close. This happened to me many years ago to the extent that it was prolonged and wet (I was too inexperienced to complain), but I definitely got worried afterwards and got tested; all OK, but a lesson learned.