OK - I finally read the Marriott email and understand this ridiculous marketing pitch...
One more exciting benefit: Save up to 40% on standard redemption pricing by booking Off-Peak rates by February 21, 2021.
So it's up to 40% off of the "Standard" points required. I should've figured this out earlier... So this is truly just a 10% off of off-peak promotion... but MAYBE every night is now considered off peak??
Somebody REALLY took liberties with the marketing speak there to make this sound amazing. I mean, I did save the equivalent of $80-$100 in Marriott points by rebooking my Swan stay though so I can't complain

Oh and by the way, it seems like this might be active now AND it's really easy to rebook your Marriott reservation and the points get credited back instantly. I'm not sure if you can book these for future stays, and if so, how far out... but it might be worth locking in some potential future trips if that's of interest to you (if it works that way).