This is a different thing to a client obtaining an assessment from another client and passing that opinion on. Unacceptable in my view. Of course, if you have told the escort the same thing that you later tell a potential client, the escort won't be surprised, but even then the potential client has no business telling the escort who passed judgment.
If you have a regular relationship with an escort, and he is told something negative about you, I see no reason for him not to push back or even tell you what had been said. You and he have the relationship, the other person is just some random.