I agree with you for the most part, but I put the cause-effect in the other order---and that's also based on how I understand the business model.
From my perspective, timeshare is a product that is
sold, not bought. Very few people wake up in the morning and think to themselves: "Today I am going to spend tens of thousands of dollars and obligate myself to decades of ongoing costs to vacation in the same place regularly, in exchange for a long-term discount." There are some--and they are disproportionately represented here in the DVC boards, at TUG, etc. but they are also few and far-between.
Instead,
most timeshares are bought while someone is on vacation, having the time of their lives. They may have spent a bit more than they do on most trips, and had to save a bit to make that happen. Then, someone promises to bottle that magical feeling for decades to come in a way that seems affordable on its surface.
Indeed, many of these purchases are aspirational; they are a way to live a little better than you might otherwise. And, DVD's Membership nomenclature ties right into that aspirational nature. You belong. You are part of the club. It's not (usually) said explicitly, but there is a subtext that Members are little bit better than everyone else there.
And, if you look at the resale restrictions, they seem to feed into this. The first round: you can't use your points on
DCL, ABD, or the Disney Collection. None of those things actually
mattered in dollars-and-cents terms, but it
felt like less. The second round: you don't get the Blue Card, the discounts, or many of the perks. These started to matter--the AP discount in particular, though maybe not any of the others. But, this is definitely creating an in-group and an out-group. The third round does this even more: you aren't even really part of "the club of owners" in the same way, because some resorts aren't open to you.
So, from where I sit, the restrictions are meant to create an
emotional sense of loss in resale as much as a real one, because the sales decision has a very large emotional component to start with. But, emotions matter, and some of those differences are material, and so there is a corresponding drop in resale price. The perception of difference drives the increasing spread, rather than the other way around.