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:>)