How to add apps to Apple Watch with Family Setup

I set up a new Apple Watch SE 2nd edition (cellular) for my teenager with his existing Apple ID. We have used the Watch app on my phone to try to add shared apps, but no shared apps appear to be available, for example, Spotify. He has an iPhone but is no longer allowed to use it, so the watch is associated with my phone using Family Setup. Everything has been updated to current OS and restarted. All restrictions on his Apple account have been adjusted after being highly restricted. How do we add shared app to the new watch with this configuration?

I was able to find four apps shared through my own account by using the App Store on the watch, but it's unclear why those are available but others are not. (I have a lot of shared apps.)