AFAIK there is no written language guaranteeing 20 reservations. There is language prohibiting commercial use - commercial means for profit.
My understanding is that many years ago DVC sent letters to folks making more than 20 reservations per annum warning them that DVC would assume that more than 20 reservations per annum would be presumed to be commercial.
Just because over a decade ago DVC decided that 20 was the threshold that would trigger enforcement of the no commercial use clause & advised a few owners of that fact didn’t create a ‘right’ to make 20 rentals for all owners.
The rental world has changed since then, it‘s grown & DVC may have decided the 20 reservation threshold isn’t sufficient to enforce the no commercial use clause & they may now have the ability/technology to use a more sophisticated approach to enforce a clause that was always there.
Edited to add: I’m linking this article
https://dvcnews.com/index.php/dvc-p...commercial-renting-limitations-amended-to-pos because it suggests there might have been language in the POS about 20 reservations back in 2007, I can’t really tell from the article.