Earlier quoted context omitted.
I'm not sure how you came to that conclusion. Words can independently change and evolve over time, while still using the same base. As a Chinese speaker, Korean very much sounds closeish and Japanese is often similar enough to realize a distant split. It is important to remember that all branches of a tree grow. China has thousands of dialects all co-evolving and we don't know which the others could have split from a…
His conclusion is sound while yours is not. Korean is not a dialect of Chinese, which seems to be your implication. Neither is it a "branch" of a tree of which Chinese is the trunk. In linguistic terms it is called a "language isolate". In the past, linguists tended to group Korean and Japanese together; I believe largely for political reasons they have been separated--but that's another topic. Korean uses many Chine…
Mongolian phonology doesn't sound like any other East Asian language I've heard: https://www.youtube.com/watch?v=OkU9Zd0LQjg