Originally Posted by
indogulf
We specifically forbid our corporate travel agent from using any 3rd party site. It's become an issue with NDC and agencies looking for more commissions.
Exactly this - corporate TA's can get [significantly] more commission by booking hotels via a 3rd party site so many try to do this. I don't know if that is what happened in this case, and I don't want to rule out a mistake on Bonvoy's part, but it seems the most logical explanation.