Following the reading of emails displayed in the global view ‘unread’, it does not operate on automatic refresh of that view. But you need to move to a different view and return to the global view. This is slightly annoying.
That is the intended behavior so that emails will not disappear from this view after you open them. They will only disappear after you move away from the folder.
From my point of view being a global view whose job is to ecidenziare only the unread mails, once they have been read should disappear automatically without being forced to leave the folder to make them disappear.