Installed Metamask Mobile v2.1.3 (53) on Google Pixel 3 running latest update of Android 11.
Syncing the mobile app to the browser-based extension at first shows all my accounts with their assigned names (mobile account names match the extension).
But when I next login to the mobile app, all my account names are displayed as generic Account 1, Account 2, … The account names are unchanged in the extension.
If I delete the mobile app, re-install, and re-sync to the extension, all the account names again match those set in the extension. Until I exit the app; when I next login to the app, all the account names are back to the generic Account 1, etc. Checking with the extension shows that I still have my descriptive account names in the extension.