China did rule over the Russian region of Primorye (where Vladivostok is) at one point. The area used to belong to China as Outer Manchuria, but was handed over to Russia as part of the unequal Conventions of Beijing in the mid-1800s after the second Opium War, along with Hong Kong to the British. While Hong Kong was returned to China in the 1990s, Vladivostok has remained a part of Russian territory since.

I don't know of anything that would entitle China to all of Siberia, however, especially as far as Lake Baikal, let alone the Ural Mountains.

I am not at all convinced by the author. In fact, I would call his speculation foolish and naive to Beijing's methodology. Why would China risk military catastrophe if they can just continue to co-opt the area peacefully and economically? what is the use of dangerously obtaining political control over an area that you already passively obtained socio-economically?