First off I suppose is a mutually agreed upon definition of VMG/VMC. The definitieons I use which I find tend to be most prevalent on the internet are:
VMC is the Velocity Made good on Course. i.e. Speed in the direction of the mark.
VMG is the Velocity Made Good i.e. Speed in the upwind of downwind direction.
Thus, it sounds as though RaceQ’s is using these definitions backwards from what I’d expect, base do the definition provided above by the developer.
Regardless of the nomenclature, I definitely want to know my speed made good towards the MARK whether it is upwind or downwind. This is especially true since RaceQ’s uses analytic predictions of where the wind is coming from, whereas the mark position is typically known with certainty.