Wii and DS ran a version of Opera browser.

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.