The watch is a new, battery constrained device. It doesn’t seem unreasonable to limit 3rd party apps for a bit while sorting out how to work with the size constraints.

I’m guessing apple will add lte support for 3rd party apps in watchos 6. Meanwhile, 3rd party apps have had the ability to make apps with offline support since June 2018. Most audio apps have added this.

Spotify....has not. What’s the holdup? Apple watch users are pretty frustrated with spotify: if all the other audio apps can do it, why haven’t they?

(Lte is an edge case: few watches have lte, and even fewer have an active lte plan. Offline audio is the main use case spotify still isn’t doing)