Yeah Hub on Android prompts you to save as a PWA. Probably because it is a webview, so exposes all native behaviour in the app. But in this context doesn’t make complete sense and probably should be disabled in Hub? (A bit of CSS could achieve and that?)
These are not “true” apps, though the Android PWA is close.
For full app experience, especially in iOS you still need:
(mainly for the real-time notifications).
Edit: that said, I like the Hub because it provides a nice directory of Discourse instances you are participating in.