This is true if you take an essentialist view of ethnicity... On the other hand, just as you assert that the Anatolian Greek-speakers were merely the assimilated descendants of Hittites, Luwians, Lycians, Lydians, Phrygians, and whoever else, I could also argue that the Greeks of Greece proper were predominantly Minoans, Minyans, and Pelasgians. Ethnicity is not eternal and trying to view this discussion from a perspective that it is just doesn't work.
How do you define for this thread's sake what would be ethnically Greek, then?