Let's try this. You know Beijing? Capital of China?
from wikipedia :
When Kublai Khan made Dadu the capital of the Mongol-led Yuan dynasty (1279–1368), all of China was ruled from Beijing for the first time. From 1279 onward, with the exception of two interludes from 1368 to 1420 and 1928 to 1949, Beijing would remain as
China's capital, serving as the seat of power for the
Ming dynasty (1421–1644), the
Manchu-led
Qing dynasty (1644–1912), the early
Republic of China (1912–1928) and now the
People's Republic of China (1949–present).
Prior to it's sinicization, it was also known as Khanbaliq. It was the Ming's who renamed it to Beiping. So first of all, the political centre of China is a Mongolian horse and cow watering town. Did you never wonder why the capital city and the centre of an Empire is at an oddly shaped appendage that just
happens to be as close as possible to and surrounded by people the Great Wall of China was supposed to keep out?
How about 8% directly descended from Genghis Khan
himself? Enough to qualify or not?
from nat geo:
GENGHIS KHAN, THE fearsome Mongolian warrior of the 13th century, may have done more than rule the largest empire in the world; according to a recently published genetic study, he may have helped populate it too.
An international group of geneticists studying Y-chromosome data have found that nearly 8 percent of the men living in the region of the former Mongol empire carry y-chromosomes that are nearly identical.
so basically, Northern Chinese can be summarized as women who got raped by Mongolians and included into Genghis Khan's harem and the men become Mongol toadies. Don't forget he's now the ruler of an empire whose word is absolute law. That's why their haplogroup map looks different from Southern Chinese. He never bothered to invade Fujian or Guangdong. He stopped in Hubei because by then he was undisputed ruler thanks to aid and assitance of Muslim artillery. Hence Southern Chinese retain some of their traditional and uncontaminated languages (and DNA) simply because there was no Mongol horde ravaging their people.
and this is his reply to the greatest pleasure of life :
"The greatest pleasure is to vanquish your enemies and chase them before you, to rob them of their wealth and
see those dear to them bathed in tears, to ride their horses and
clasp to your bosom their wives and daughters," -- Genghis Khan
you can slowly take the time and enjoy reading a fuller version here :
https://www.dailymail.co.uk/news/article-456789/Genghis-Khan-The-daddy-lovers.html
He was very efficient at impregnating women and he encouraged his Mongol horde to do the same. Not that they needed any encouragement...
As for Southern Chinese being sinicized, it's true. Southern extremities of China were not 100% Chinese. But that was far earlier in the game. They became sinicized. And this is the gene pool / people that sinkieland comes from. But they were not Mongolized genetically nor culturally as Northern and plains China was. As to your argument that Mongolians got assimilated, that's true too, but genetically they still retain unique markers that distinguish themselves as Mongolians and not Han Chinese. So if you will, they became chopstick using Mongols. If that alone qualifies, then why not Middle Easterners who speak Chinese and follow Chinese culture?
Anyway I hope that info helps. If not, I can go digging around for more.