First of all, I'm not so sure the impetus for the recent change was either punitive or designed to help direct sales. For one thing, I don't think the resale market is that much of a competitor for DVD. Most prospective buyers don't even know resale exists, and whatever impact it does have is offset somewhat by the sales point that your DVC will be worth something when you want to get out.
Rather than a shot at resale, I have a nagging suspicion that the root cause was the increase in AP prices raising the ante for DVD to provide those perks to DVC owners. We don't know what they pay, but I think it's very likely that DVD pays something for every DVC AP sold. The same is probably true for the other discounts -- it's not very likely that the merchandising and dining folks are just giving stuff away to DVC.
If my suspicion is correct, a logical response would be for someone to ask, "Hey, wait a minute...we're paying a cost for people who didn't buy from us to have these discounts! What's up with that? And how can we a) reduce our costs and b) make sure we're only subsidizing our own customers?"
We may never know, but I'd bet there is some other reason for these changes.