Not quite correct. E-ticket interline and baggage interline agreements are two completely separate things.

Having an e-ticket interline agreement means that the first carrier can issue a ticket containing a flight on the second carrier. Having a baggage interline agreement means that the first carrier can check a bag through to the second carrier.

In this case, VX does not have the ability to book reservations and issue tickets on records containing a CX flight. (That is, you cannot go to VirginAmerica.com or call VX and book a flight to Hong Kong on CX. If you wanted to book a flight involving VX+CX, you'd have to do it on Cathay's website, since Cathay does have an e-ticket interline agreement on VX.) However, nothing is stopping VX from checking a bag through to CX regardless of ticketing status, except for internal policies at VX or CX.