I agree with you in principle, but where the rubber hits the road is if you limit it at say 400 points, some people will set up a few different entities that each have 350-399 points— Yes, there are a few giant entities, but there are dozens of people renting 1000-10,000 points a year in this manner who would be incentivized to find some shell owners if there are no rules below a certain threshold.
Honestly, given current technology they could probably scrape the major listing sites and social media pages and actually determine what people are trying to rent for with very limited human effort, that would be the most accurate—but I also think they could say that any rooms less than say 25 points per night cannot be spec rented, it would nip the problem in the bud if you can only change names on a confirmed reservation for the less profitable categories. By zeroing in on the area there is clear abuse, they could limit high profit rentals. Nobody is making $30/night renting 1Bed at most (all?) resorts.
I would be ok side, but the issue with this approach is that it’s very labor intensive for Disney.
I still think their primary concern is not having cheap studios undercutting bookings at deluxe and moderate resorts. So stopping all spec renting and especially spec renting of low point rooms is cleanest with minimal effort.