Happy days! Email notifications are finally fixed again. Not sure if that's a Android 11/OneUI3.0 thing, or just an email app update and is well timed.
About a month or 2 ago, tapping one notification for an email would dismiss all email notifications for that account. It meant you'd probably forget you had an unread email, because going "back" or deleting the one you opened would take you back to the home screen.
Finally tapping a notification for an email, leaves the other notifications alone.