EDIT: But I think Villabruna is a mixture with a lot of Vestonice as it simply makes more sense. The culture was called Epigravettian for a reason.
That would mean that due to its absence in WHG the Basal Eurasian (rather than the Ancient North African) component is either a relic or greatly inflated, wouldn't it?
Going back to the assumption that Villabruna descends from a rather unmixed population, is it possible that there was a super isolated Paleolithic population somewhere in Europe or the Middle East (on islands, in mountains or something)? Sounds stupid I know, but as it stands I find it difficult to imagine that the Proto-Villabrunans would have been freely roaming the Balkans and Anatolia without acquiring either Basal Eurasian or Sungir-Vestonice admixture.
I'm thinking of something like the Corbeddu cave of Sardinia perhaps. Although it's much more likely that those hunters were similar to those on the mainland of course.