Anyone who knows them enough to hear any negative, knows they have very little experience with horses. I wouldn't worry too much. Almost any horse will take advantage of a novice.
This reminds me of a kind of funny story. We're going back about 30 years now....
My riding coach had a fabulous little Shetland named Tonka that literally taught hundreds of kids to ride (including me!). She was gentle and tolerant of all the silly things a novice rider can do. However, as soon as a kid learned to post at the trot, she knew it was time for her to move on, and she would start bucking. It was no big deal to us, because we all knew what it meant. It was sort of a rite of passage - when Tonka started bucking, it meant you were becoming a better rider!
Well, we were at a show one day and some lady none of us knew saw Tonka getting a little fidgety with one of the students. This woman grabbed the reins, told the girl to get off, and informed us that she would "show this pony some manners". Well, you can all guess what happened - this woman was immediately sent ass over teakettle!
By that time we had scurried off to get our coach, who was not happy! I'd never seen her mad before, but I did that day!
Maybe these people already know it was thier own error and won't badmouth the horse at all. I was the 'buyer' in a very similar situation years ago. The horse I bought was still fairly young and green but she was bomb proof and excellent with kids on her back. Really good horse...till green 'me' bought her...well lets just say she figured me out from the get go and things got pretty scary. I didn't over correct, my mistake was that I didn't correct at all, just became afraid of her. But I knew it was ME, not the horse, because as soon as someone experienced was around her she was fabulous!
So maybe these people know as well that they are too inexperienced to handle a horse. I tell you, I will not do horses again...I just don't have it in me:>)