Hmmm... I have always been taught that matcha is directly from China, coming over around AD 1000 pretty much exactly as is today. Tea ceremony changed big time in Japan, but the matcha itself is always credited to China. If there was a stopover in Korea in between that transmission, it wasn't told to me nor is it recorded in any of the writing I've read on the matter.

Anyway, I'm at work so can't watch your video, but will do so as soon as possible and may comment more at that time.