I do feel that there is a wide variety of Japanese greens around.
However, the name of Japanese tea usually only refers to the way in
which it has been cultivated and processed (sencha /kabuse-cha
/gyokuro/ hojicha), and not to the unique characteristics of the tea
itself. Whereas all senchas have the same name, they have a significant
diversity in flavour.

I do not have a preference for either Japanese or Chinese greens, but I
tend to drink Japanese greens during working hours (100g a week, I am
addicted) and Chinese greens/oolongs (mostly oolongs) outside those
hours. Indeed, Japanese greens have this vegetal freshness, whereas
Chinese greens tend to be more complex.

Cheers,
Erwin