Client reviews wouldn't likely be on terb, it would cause too much drama from angry trolls or hobbyists who didn't receive the reviews they wanted.
The SPs then would have 3 options: review no one and stay out of drama, review only positive experiences from their personal handle, or have to create a fake handle to write reviews to avoid backlash (isn't that what many terb guys do so they can critique?)
The board culture at times is already a pissing contest between long time members who think they hold clout and super reviewers who think because they can afford to book often and review often they are more valuable members. Any threat to this would cause problems for not only the SPs but the moderators too and clients wouldn't want to pay to support terb so that's extra work for mods to deal with (complaints and potential drama)
If a hobbyiest received a negative public review then he is less likely to ever provide his handle again or give screening info or take it out on that SP or the next SP if he's particularly bent out of shape. So this doesn't make it safer for SPs either.
If it went the way of flowery kissing up reviews then it wouldn't really mean anything and other guys would be fed up reading it and SPs would probably tire of having to write such things to ensure they don't rub anyone the wrong way.
If there was another board, and it was anonymous - maybe. But we already have a problem with SPs not passing on blacklist info as it is, most of the time it's kept to themselves, so in reality few SPs would want to spend more time trying to figure out their clients board handle and then publicly reviewing them.
Not to mention how many guys get jealous even on twitter when they see their fave interacting with another, as soon as there's a record of everyone who's seen her it can escalate problems. I've heard stories of hobbyists even fighting at Spas when they see a guy they don't like and know he's going to see his fave and he has to wait.
While it would initially maybe hold some guys accountable it would probably deteriorate quickly, be criticized as untrue if the Sp had anything bad to say (like he was a little too rough or stayed over time) and then guys would get even more secretive and possibly it would hurt the SPs business or put her in danger if someone was really mad at her. Don't underestimate a jealous or scorned person, it's not pretty.
Not every client who just shows up pays and showers is a 10. That should be the bare minimum for a decent client. If a client is polite, kind and follows your boundaries and respects our time well then that's a little more likely to make them a very desirable client. Tipping is never expected, it's only occasional so that can put you over the top, but that alone doesn't make you a great client, nor does it mean anyone who doesn't tip wouldn't be a great client.
The less desirable aren't just those who have terrible hygiene, but could be bossy demanding ones who want to direct the entire session, go way overtime and won't leave, show up super late and expect their full appointment time, have really scratchy stubble and grind it into you, are too rough and bite/pinch too much so you're sore etc.