This has been so confusing right from the start. I haven't been able to make heads or tails out of what they post and what they say when you call them, other than the only consistency has been in what my account shows several days following all the cancellations processed within 60 days of check-in and prior to whatever date is posted on the days I called. Between original reservations being booked/cancelled and replacement reservations being booked/cancelled, my account has about twenty affected reservations and I've spoken to Marriott reps who've told me wrong information for at least a third of those. That's the only good thing I see about this policy ending before COVID19 is resolved - maybe I won't be bonking my head off the desk so many times next year.
Over the years we've been able on the Marriott forum to piece together while they're happening a few different changes to Marriott IT structures, but mostly they don't make sense until after all is said and done. With your Vistana accounts I think I'm seeing that they implemented this change and realized too late that it reverted existing points status incorrectly, so last night they reversed the change bringing that status incorrectly all the way back to the normal 60-day cancellation terms. Now they have to do whatever manual step they've had to do all along to bring that status to 120-days again, followed by whatever they come up with that will revert upcoming cancellations to the normal terms while not impacting all the existing C19 cancellations. Piece of cake, right?