I was a child in Greece, 1979–1983, and maybe not the best informed source of information on attitudes toward the North at the time. I know that in socialist circles, the notion of “The Northern Threat” (ο εκ του Βορρά κίνδυνος) was often ridiculed—surely everyone knew the Turks were the real enemy, within NATO, and not anyone in the Warsaw Pact.
Tito’s vague plans for a Macedonian Federation in the Greek Civil War did not figure in the popular imagination. Any notion of an actual Northern Threat in popular culture, in my experience, focussed on Bulgaria, with which Greece had actual hostilities in the early and middle 20th century, not Yugoslavia. I was in Crete though; Dimitra Triantafyllidou may have had a more granular understanding, being closer to them.
There was little rhetoric of Brother Serbs and Fellow Orthodox at the time; but there was a clear sense that Yugoslavia was the least bad of the three northern neighbours, and that we didn’t mind Tito. Tito’s death in 1981 was certainly a big deal.