Oh it gets better. If you look at the appx package names for "Groove music" and a couple others they're still Microsoft.Zune prefixed
Source: former dev on the team.
Disclosure: Microsoft employee, but not on Groove (or anything related to appx packages for that matter)
I work on a codebase that still carries product names that stopped being meaningful almost a decade ago. No value in renaming across the codebase and it’d be expensive because of how much code has to be touched.