Actually, it's not a deeded interest. I went back to the document set from my rescinded purchase of WPORV twelve years ago (which is when I learned about TUG and rescission and resale, but that's another story).
The "SVN Owner Membership Agreement" is a contract -- a "separate and distinct contract from any contract with any developer or seller of a vacation ownership interest or vacation membership plan" . It is a contract that "shall be governed by, and shall be construed in accordance with, the laws of the State of Florida" (para. 12) -- something that could not be part of a Hawaii real property deed. The contract is between SVN and "Owner" -- not a deed conveying something to an Owner. This Agreement doesn't reference the deed, CC&R's, or any other recorded document (and the deed doesn't reference the Agreement).
But the best is "The terms and conditions of the SVN Rules [which are elsewhere incorporated by reference] are subject to change by SVN Operator in its sole discretion without Owner's consent, including all SVN fees, benefits, and reservation priorities and procedures." (para. 16j)
So Vistana holds all of the cards. It would be incredibly stupid of it to change the rules, but it can. My concern is a corporate takeover (suppose Apollo buys ILG?); the new operator will try to squeeze out more profit no matter how. Those of us who have been active in timeshares for a few years have seen enough spinoffs of timeshare companies and enough true sleazes in the business that the possibility cannot be ignored.