Earlier quoted context omitted.
by this standard, Japanese would be a variation of Chinese
Italian, French, Spanish, Portuguese, and Romanian are all directly derived from Vulgar Latin. Japanese is a linguistic isolate, perhaps distantly related to Korean (which is also a linguistic isolate). Japanese borrowed the Chinese writing system, and a little bit of vocabulary; calling Japanese a variation of Chinese is akin to saying English and German are a variation of Latin.
It'd be more like saying Finnish or Hungarian are a variation of Latin or German. Some small amount of shared vocabulary (and maybe phonetics) due to proximity, but no more.