Maybe, but I've watched someone who places horses with adopters (horse rescue, not a for-profit-sales barn or antyhing) and I've seen her more than once after a few minutes be able to say, unequivocally: "This is not the horse for you. I am not convinced you're experienced enough to handle this horse." Or something of the like. It's often very easy to tell who is experienced enough (especially when we're talking about a yearling here and not an older horse) to handle a young horse and who isn't, even just from talking to them, without even seeing them handle any horses. And, in my mind anyway, I'd have to think an ethical seller wouldn't sell a young horse to two people who didn't obviously know much about horses, even if they claimed the horse would be going to an experienced home or something.
Just to play devil's advocate here, whoever sold the grandparents the horse may have had no idea the people didn't know what they were doing.