Yes, the extension to 1923 is done by the people that have faced genocide till 1923 once the Great Powers got Syria (and thus stopping the massacres of Assyrians) from the Ottomans.
Why should I give a citation when you explain it right after asking the citation?
Anyway, here's one I grabbed from Wikipedia:
http://www.hawaii.edu/powerkills/SOD.CHAP5.HTM
"In this post-WWI period the Turks killed overall probably 878,000 Armenians and Greeks, or at least 665,000 and even perhaps as many as 1,156,000 in total (line 435)."
Now, divide that by three because it's quite ludicrous, and you have alhoon's estimation out of his deeeeeep understanding of history of 250-300K dead Armenians and Greeks post WWI.
Following that totally legit and reliable source, we get to the conclusion:
"Finally, in the remainder of the table I calculate the democide rates for the Young Turks (lines 636 to 637) and the local Nationalists (lines 640 to 641). Per year the Young Turks killed almost 1 out of every 100 of their population (line 637). The Nationalists, however, were far more vicious. For the population they controlled they murdered 1 out of every 38 per year (line 641)."
So, there you have it! If we ignore the weird numbers that would have us think that more or less every death from 1919 to 1923 was a result of Kemal's guys killing people (if you read the tables, he makes an estimation of how many Muslim Turks they killed) ignoring food disruptions, disease and other hardships of a collapsing state or people fleeing and not informing their current census office they were fleeing across the border... our reliable source paints a clear picture:
Kemal's nationalists were about 3 times as violent as the Young Turks.
Look, all jokes aside, the Nationalists were considered by our historians to be about as bad as the Young Turks. They killed less of us because less of us were around to be killed.
Here you can see a more reliable estimation: 260K dead by Turkish forces during Kemal's time. Nureddin Pasha is said to have killed ~12K Greeks, many of his crimes are recorded and I didn't see Kemal executing him.