You don't need to convince David, he has no control over the transaction, David would need to convince the owner. And why should David do that? Why should the owner do that? David's business model works because he offers owners the ability to rent out their points with almost no hassle. If he starts to create hassle for the owner or himself, then the business model falls apart. Owners willing to deal with the hassle rent out their points as individuals and pocket a few more bucks. If I'm going to have to deal with David or his staff trying to convince me to be a nice guy, why am I using David?
Plus, you have zero information to make that statement. If the points expire on October 31st, at this point, your statement is not true at all. In March it was more true, but you were still on the seven month window for points expiring, which means that the points are worth less, and availability will quickly get spotty. If points were borrowed, that's going to increase risk.