Apologies for late reply - my VAM account was broken for a week (someone in Veritas decided to change my logon email address to something else that does not exist).
The document helps in a way, but the promise to keep on releasing updates for the Appliance did unfortunately not realize...
We were told by Product Management :
"Sadly BE16 won't be supported on the BE3600 appliance.
We can offer a migration to 5TB Capacity if this helps? "
Seems BE15 was the last software for the Appliance.