The term "Tatar" or "Tartar" is used in several ways. This usage refers to "Tartarians" as the Chinese that the Dutch were actively trading with during the 1600's.
These are not Kazan Tatars.
The multiple use of the term Tatar serves to confuse everyone, including many Tatars. Tatars are not Chinese Mongol, or Russian. Tatars are Turkic Muslims, with populations all around Russia, with sizable numbers in Moscow, St. Petersburg and of course within Tatarstan.