Actually Tsushima was drawn but it may have been drawn because it is located at near Chosun. One can't claim ownership from this kind of map.
When the local government of Tsushima sent treasure (gold) to the Imperial Court of Japan in 701 AD, emperor was glad to have the gift and gave the name of the era Taiho (大宝, treasure）. So at least Tsushima was Japanese territory in 701 AD. And in the 魏志倭人伝, the old record of China (陳寿 233～297 AD) also referred to Tsushima as a part of Japanese counties. So the scholar's theory is out of question.
By the way, in this map Usando was drawn at the west of Ulleungdo. This map was another proof that Usando was not Liancourt Rocks. The professor may have shot his own foot.