But as far as E-V13 is concerned, there is absolutely no evidence that it is native to Greece or the Balkans. In fact, I have made a
new phylogenetic tree of E-V13 a few days ago and the variety found in the Balkans fall within the S2979 branch, which has no less than 8 sister clades at the same level. The other branches are found mainly in northeast, central and northwest Europe. All of the branches at that level date from approximately 4000 years ago, when the Bronze Age was spreading from central Europe to western and northern Europe. This was before the Mycenaeans arrived in Greece and the Italics reached Italy. E-V13 itself has a TMRCA of 5400 ybp according to Yfull. That's when the Steppe PIE started invading the Balkans.
I therefore have to reconsider the history of E-V13. Seven years ago everybody thought it came with Neolithic farmers from the Levant. One E-V13 was found in Neolithic Catalonia but nowhere else. That's when I proposed that E-V13 was actually native to southern Europe, a descendant of a group of E-M78 that had crossed directly from North Africa to Spain or southern Italy. This might still be correct as E-V13 was indeed present in southern Europe but was apparently not part of any Near Eastern or Balkanic Neolithic cultures. What differs now is that E-V13 wouldn't have spread all over southern Europe during the Mesolithic and Neolithic, but only during the Bronze Age. The only way they could have done that was by 'hitchhiking' their way with the Indo-European migrations. The reason why E-V13 became so much more common in the Balkans than elsewhere would just be by chance, either genetic drift or a founder effect in some dominant and particularly prolific paternal lineage.
Unfortunately I have very little information about the deep E-V13 subclades in Italy itself, but in all logic there should be more variety in the north as V13 would have come from central Europe with the Italics and even later with various people assimilated by the Goths in central and southeast Europe before they reached Italy. In the south, E-V13 should indeed be the same variety as in Greece.