PS5 is trailing behind PS4 launch aligned in US, UK, France, and pretty around the world except Japan since PS4 was released later then everbody else.Yes, Switch is much bigger (per capita) in Japan. Their society has pretty much moved to exclusively mobile and handheld games.
PS5 is still the fastest selling console worldwide, even if Sony isn't focusing much on Japan. It IS still sold out everywhere in Japan (just like everywhere else in the world).