It is true that software is not their strongest skill.
Besides, for years, japanese people had its own way in dealing with GUI with little concern to the rest of the world.
They had fantastic cellphones... for home market only (maybe Korea too).
They had an online social network 10 years before FaceBook... only in japanese and with a weird ergonomy.
And lately, instead of expanding their skills in a more global approach, they have massively adopted foreign techno (the boom of iPhone/Facebook was particularly impressive in the late 2000s).
Same in music production : they remain strong in hardware, but in soft, musicians have massively adopted NI, Logic, Steinberg, UA, etc.
That said I wouldn’t be surprised if some remote editors keep developing plugins.
But I saw nothing of this in music shops & when I talk to local musicians.
That said, gear wise, Japan is like heaven : so many local brands for good instruments (notably stompboxes).
(I precise that I’ve been going there quite a lot and I’m half fluent in japanese language)