That’s accurate. Note that “diehard” here is not metaphorical, it’s literal. The Greeks literally died massively for 100s of years defending the Byzantine territories e.g. Even after 1453 (fall of Constantinople) the Ottomans couldn’t take over Crete for the next 2 centuries.
According to the original byz sources of Phrantzes or Sphrantzes (Φραντζής) the Cretans where the last to abandon the battle defending Constantinople and among the first rising against the occupation (1771). The Cretan style (& music) remains the symbol of “national” in Greece.
That’s why the most famous Byzantine national song (ΑΚΑΘΙΣΤΟΣ ΥΜΝΟΣ, Τη Υπερμάχω Στρατηγώ) remains the strongest inspiration for Greek military, of course in greek language, lasting from 626 AC! Byzantines were in the most LITERAL sense DIEHARD Greeks.