How long has it been that you've been able to earn points on Vistana stays?
I recall about 7 years ago being on a plane to Orlando, booked at the Hilton GVC at Sea World, and sitting next to someone who worked for Starwood. He (jokingly) asked why we weren't staying at an SPG property, and I told him that they didn't participate in the program and it was a dealbreaker for me to not get points for a stay.
So I'm kinda thinking I was personally responsible for the change.