Does it even matter? The reality is that most weeks at this resort, with the exception of Platinum weeks and perhaps some 3BR Gold weeks (esp seafront), already have resale values between $0-$2500 (asking prices at:
https://fabtimeshare.com/marriott-vacation-club-resorts/playa-andaluza/) and a sale would net the seller even less. For Gold weeks that's already 60%-80% less than the purchase price, so, if they are worth zero in 30 years, should we care? It's not like it's any different with Trust points... even if you buy them resale you lose 50% because of the $3/point "nuisance fee," which has tripled in the past 12 years and may or may not go up some more in the next 30.
People on this forum are relatively informed buyers and would make a purchase like this because they want to add points for a variety of reasons and this alternative option offers the equivalent of the points product at lower upfront costs, lower maintenance fees, and may allow the enrollment of other resale weeks for certain purchase amounts. The fact that it might expire in 30 years is neither here nor there to me, especially because the alternative points product is would likely also be worthless in 30 years anyway and would most likely be a greater liability to my heirs.
I'm not saying it's not important to understand, but I don't think it should really affect the decision to purchase. If you are considering adding points, this is likely one of the better alternatives, IMO. Not necessarily this particular deal, but a Spain week (personally, I would go with a more expensive one, but better point/MF ratio) vs. resale points in general.