not the dining offer
This mystery bonus does appear to be associated with the dining offer, but in an odd way.
I got the dining bonus on a stay in May.
Then I stayed at a different HGI in June, and this "All HGI" posted with those points, but referencing the different HGI I stayed at in May.
Happened to be on the phone with CS on another matter and asked what it was. They said it is an error that causes duplication of the dining bonus, but stated as the "All HGI."
So clearly they're aware of it. But looks like they havn't gotten around to fixing it. Take you time, HHonors.