The iTunes Store, which was embedded in iTunes, sure was a webview, but I don't think Apple Music ever was a webview?

(Except maybe the "Home"/"For Me" pages which are just "discovery page" extensions of the store and the Apple Music service that's built on top of it)

The macOS one descends from iTunes and the iOS one descends from the original iPhone which sure as hell wasn't a webview.

It was, you often could see JS error messages or weird rendering errors / flickering (Also some other mentions: https://news.ycombinator.com/item?id=20892650).

There's also some parts of System Settings that were always web views, which I always found surprising for a company trying to make the case for native apps.