Vanilla themes not listed in theme editor

Hi, all

Our SAP EP is 7.3.1 SP6. When I go to the content admin -> theme editor, I only see 5 themes listed. However, when I go into the portal content -> themes folder, I see theme like sap_corbu, sap tradeshow plus, etc that are not in the theme editor. I log on as "administrator" and this is a vanilla installation. So it is not a permission issue. Can you shed some light on why?

Thanks

Jonathan.