There is no reason to believe the VS separation (If at altitude) included the HS, elevators, or for that matter compromised the integrity of the aft bulkhead. So pressurization may well have existed at impact.
I for one agree with BOAC, as those who are vets of the prior threads know. I have believed in VS separation from the beginning (perhaps as early as initial upset). The location in the initial search of the port elevator suggests a separation also of the Tail feathers, but again, not necessarily at impact.
The early conclusions of BEA notwithstanding, to entertain that the VS was aboard at final impact challenges logic, as the condition of the sea floor debris would suggest. The galley stack included, the VS and cabin parts were no where near the final impact zone, as the extent of the destruction suggests, from the new photos. It also requires a substantial horizontal ("Thrown forward" and clear of) component, unlikely to have happened even in consideration of BEA's conclusion.
The condition of the VS has been exhaustively discussed prior, and this is not an invitation to continued speculation, at least by me.