notice in your first link, the greece+balkans had 5M in 500AD, lost 2M by 650AD and gained again, mostly likely when the slavic migrations happened after 650AD.
What was the 2M loss, Romans or Goths departing??
Christians and Diseases
Christians
The greatest massacres of Greeks and depopulation had hapened by Christians and diseases, especially after 370 AD to 800 AD
estimation of 4 000 000 Greeks to be executed in the name of Jesus,
search Skythopolis, Σκυθοπολις,
today the name is Beth She'an
read the Constance B' orders and laws,
Placuit omnibus locis atque urbibus universis claudi protinus templa et accessu vetito omnibus licentiam deliquendi perditis abnegari. Volumus etiam cunctos sacrificiis abstinere. Quod si quis aliquid forte huiusmodi perpetraverit, gladio ultore sternatur. Facultates etiam perempti fisco decernimus vindicari et similiter puniri rectores provinciarum, si facinora vindicare neglexerint»
"Res Gestae Libri XXXI"
the story is saved by Αμμιανος Μαρκελινος
Ammianos Marcelinos or something like that
NAZI camp were nothing compare to it,
Holy inquisitors will Envy
a witch hunters paradise
the stories also exist in Christian chronicles of Σωζομενός
about the act of Pope of Alexandreia George Γεωργιος,
Greeks hide in North Balkans but Byzantine hired Goths and Alarih who burned down 80 towns for more than 40 years
http://xemandrios1.blogspot.com/2011/01/blog-post_1484.html
and since you do not understand Greek read in English
http://ethnikoi.org/katastrofi.htm
http://ethnikoi.org/persecutions.html
Greeks moved to West Roman parts but and there Ονουριος Honorius is the same
the massacre last Long enough, even after the Schisma.
DISEASES
Just consider how the above effect the Genetical Data,
and also loss of Medical, since the only Doctor is 'God' and the one who use medicines is a witch, a pagan, only pray save and cure, all the rest knowledge are Diabolic
only in Athens we have 2 depopulation from diseases until 911 AD and one 3rd at about 4rth Crusade.
But these diseases Saved the monuments since to many local people become a taboo to destroy them cause after a disease comes.
590 Era vulgaris
Rome
Pope of Rome Gregorios (the great) order to burn down the last working biblioteque the Apollonian
the last storage of ancient texts
the total estimation of Greek Holocaust is estimated 4 000 000 by some to 19 000 000 by others,
It is the biggest genocide ever done.