We don’t force add meta on the DiscourseHub app for users. I suspect you did click the + button from the Discover screen at some point and then it got added there.
Yes, think of this as the app saying “you had a session with this site in the app, it has gone stale, log in again to resume where you left off”. The wording is tricky because the feature allows the user to log in with the site’s enabled login methods in the DIscourseHub app. But basically, if you select to continue, you will be able to log in with Google in the app, and then you can use meta in the app as that logged-in user.