Well, Microsoft pioneered with that earlier. Win98, or was it 95b, merged the filesystem Explorer with Internet Explorer and came up with ActiveDesktop.
Which was very cool and accessible as a kid, I have fond memories of it.
I remember renaming .html files as .hta and thinking I was a developer.
I was kind of ready to call BS on this, Nintendo is usually a little more careful with these things. But, you are absolutely correct.
Nintendo uses web UI a lot. The Switch eShop is notoriously a web app running on WebKit without JIT. The Action Guide in Super Mario Odyssey is web despite everything else being native.