A folder with PST file's name is not appearing in user's AM mailbox when pseudo root option with filename option is chosen
Archive Manger shows only single message within single mailbox. The behavior is by design and due to single instancing.
If PST is required to be shown as separate folder please uncheck "Add PST contents to owner’s mailbox" option. This will create a PST type mailbox assigned to the owner specified during import process and appear as additional mailbox on AM web site.