Greek-like or Albanian-like samples can even be found in Romania before the Slavic period and were even found in Hungary for example.
Ancient Greek samples don't cluster like modern Greeks anyway, they were extremely Southern. And the one more north in Greece was closer to Kosovo Albanian rather than other Albanians. There is also variation in plotting among Albanian populations with some Southern Albanians almost being Sicilian like and not Greek like, they are even more southern than some mainland Greece. In Greece there is also some Slavic influence depending on the region, some areas of the Peloponnese have the least Slavic influence, there were also Vlachs that settled Greece, Bulgarians, Arvanite. Those samples in Croatia don't cluster like Albanians but saying that they are not ancestral is nonsense maybe not ancestral as in recently but it obviously represents the same wave of Indo European settlers or whatever they were, and in some cases some of this autosomal DNA doesn't seem to of been entirely washed out, some of it was inherited like 50%-77%. They clustered like Italians but some samples in Montenegro, close to the border with Albania, clustered like Iberians actually. Also the Iron Age in Bulgaria was very southern. I wouldn't be surprised if samples from the Republic of Macedonia turned out to be Greek like or Tuscan like for example or samples from Kosovo. Or maybe even southern than that like the IA Bulgarian. Neither would I be surprised if they clustered like Italians.
There is also the question of the origin of the Romanian/Aromanian language and their native Balkan ancestry actually seems to be similar to Albanians or almost Greek-like, Tuscan like etc depending on the person. Slavic Macedonians also seem Albanian-like in a lot of cases, it could also be due to intermixing.
And Albanian language has very little Greek influence except for some Ancient Greek loan words, and Greek mythology. It obviously suggests that Albanians did live close to Ancient Greeks at one point but during the Roman period were more influenced by Latin while not being Latinized. The Mat region had the least Latin influence and was at the border of the Jirecek line. Nothing suggests an origin more Southern than that yet you also have Albanians who believe in the whole ''Epirote'' theory. While the Albanian homeland was not too far away from the Epirote in this case and Albania was referred to as Epirus by the Romans.
There is also mention of ''Albanos'' and Albanoi in Macedonia. And they are mentioned in Southern Albania. The question is more where did the language itself survive, or the people that came to be known as Albanians, rather than where did the proto-Albanians live since they could of lived anywhere, then I agree that the language might of survived somewhere in Northern/Central Albania where also the Gheg-Tosk split happened. Or between the Mat and Shkumbin river. It's possible the Illyrian population that lived in these areas were indeed like modern Albanians that live there today.