It wasn't found in Greece but North Macedonia. The earliest diversity is Anatolian and earliest examples of auDNA heavily Anatolian.
J2a-L26 is a macrohaplogroup designation. You can't argue with macrohaplogroups whose formation and TMRCA lies in the Paleolithic, the conclusions will be erroneous.
You can check the Albanian J2a-M410 branches on Rrenjet, lumping them under macrohaplogroups doesn't serve any purpose. J2a-PF5252 for instance being found in Bronze Age Italy is irrelevant to Albanians because most Albanians belong to different haplogroups under J2a-M410, which is a macrohaplogroup.
Neither in Balkan Neolithic derived J2a-Y7010 branches in Albanians nor Roman era Anatolian derived Albanian branches will you find clades shared with Greeks.
For further reading:
https://rrenjet.com/j-m410/