"With Points Advance, you are reserving your room, but your rate will be subject to change until all required points are earned and is the points are attached to your reservation." (emphasis, mine but language is Marriott's)
Coming September 14: Off-Peak and Peak Point Redemption Rates Blog Post created by communitymanagers on Aug 15, 2019
If you reserve and submit points or certificates at booking:
"You can rest assured that any reservations booked with points made prior to September 14th will reserve the Standard redemption rate. If you need to change that reservation after September 14th, you’ll receive the available redemption rate when you rebook."
As the Points Advance video example explains: Redemption can be at Off-Peak (lower) than when you reserved OR Peak pricing (higher). YOU PAY POINTS IN PLACE WHEN YOU REDEEM next month, next year, etc.
5 Points Advance reservations are allowed
Only 3 Points Advance reservations at any time will be allowed
ALL will be charged at prevailing rate when the points are redeemed - Peak, Off-Peak or when they trigger 15 days before. C