Originally Posted by
Tanic
That's a recent BonvOY "enhancement".
No, it is not. The restriction has been in there since the new rules were published effective August 18, 2018. Has been much discussed in numerous other threads since.
While no doubt disappointing for those who regularly book through OTAs, it's no surprise. Marriott was the last major chain to grant benes on OTA rates. It's also understandable that they want to drive bookings through their own channels given how much more money they make that way.