I don't know exactly how common it is, but given thre reality of human nature, it will always be present to some degree. A more subtile variation is a provider not finding time to make an appointment with a client she identified as the source of a less than stellar review. Guys figure that out and inflate their reviews in order to be well received for future visits.

I've found good correlataion over the years between scores and perfomance, not quite as much as looks, but you can always see the provider's photos and judge for yourself.

If the provider emailed that info to you, I would forward it on to TER administration.  They are concerned with the legitimacy of this site, and trying to coerse high scores this way is counterproductive to that goal.

If a lady said she'd see me only for a good good reviews,  I'd figure she must not deserve it and stay away.