I have to agree with Carmen, allowing people to leave reviews for people they do not have a professionally binding interaction with is troublesome. I've had meet and greets with clients that were extremely rude about me declining to book their dogs for whatever reason (aggression, age, not house trained etc.). The meet and greet is in place to ensure a good fit before booking. If it's not a good fit for either party, neither party should be able to limit the other's ability to do business through Rover. This opens up the possibility for sitters who reject bookings to be given negative reviews for simply saying no. On the flip side, it opens up the potential for the owner to receive negative comments for sitters who were passed up for another option.
Now, if there is something concerning that is noticed at a meet and greet, Rover support can still intervene (as both parties are members of the Rover community). For instance, at a meet and greet, I came into contact with a couple that were clearly neglecting their outside dog. I'm talking, chained to a fence in the Texas summer heat type of neglect. I refused the booking, contacted Rover support, and received support as I contacted the local SPCA. As an owner, if you noticed unsafe/harmful behavior of a sitter while at a M&G, you could contact Rover support as well.