Few providers would likely care to do this. For the most part, most are in this for reasons other than sampling and comparing the sexual performance of a variety of men.
From what I've heard, as well as what I've seen up closer than I probably should have, this is about tolerance. How much unpleasantness can one escort tolerate from a particular client. One year one escort told me that it was nauseating whenever one particular "regular" client went down on her. But like clients, escorts also have "ATFs" they actually enjoy fucking and/or spending time with.
Most would be unlikely to want to spend their precious free time writing reviews of guys and almost all would be uncomfortable disclosing their honest views publicly. It would likely make their regulars (and prospects) either jealous or angry.
One now-retired escort fulfilled a personal fantasy of mine and wrote a "your eyes only" review of our last (and best) session. I have not, and will not, share it with anyone. But what fascinated me was not the content of her review but her perspective. She focused on her plans for the session, her emotional responses, and her thoughts about how I responded to her actions. It was not mechanical or as visceral as the reviews guys typically write. In this case, we knew each other very very well (over a year) and the session was 75% of her dominating me (blindfolds, toys, etc.), as we had planned, which was different than how we usually got down. Again, what was so refreshing (and embarrassing) about her review was that it was mostly "Big Head" rather than "Little Head" (or rather it was mostly "Big Heart"). Unfortunately, I doubt I'll ever have the chance to be with her again given her retirement. We had amazing times together and reading her review of our session always brings huge smiles, and major wood.