From what I gather, Mark's numbers come from a survey. Incomparably better than the ones I have access to from Itch's metadata. Still, those are the ones I've been using and will use in the future, so here's the full GMTK's chart:
Tag-wise, Godot is already ahead of Unity by almost 3% (41 to 43.7) Using Tools, the distance is even greater. At least now, I know how much more metadata Godot users add than Unity ones.