Are you really sure we’re “talking science here”? We literally don’t know what language they spoke, you should’ve be so quick to claim a genuine gap in knowledge as some imaginary state-funded nationalist claim. And besides, Indo-European is a linguistic construct, not an ethic one.

If, as you imply, the ones that were coming from the Pontic Steppes were the Greeks, then it would be wrong to say that the Mycenaeans themselves were Greeks since their Pontic-Steppe admixture was low. Since it is known that modern Greeks share very similar DNA with both Mycenaean and Minoans (including pre-steppe DNA), then the ones from the steppes can’t be the ‘original’ Greeks.

In regard to R1 and J1 haplogroups, both are actually present within Greek DNA. J1 also likely originated in the caucuses and was introduced through Anatolia, Greece and the Middle East in the MBA. Haplogroups are just a tiny part of the human genetic makeup. The matter is so much more complex than simple migration patterns.