Hmm, I think he is. In his article about Australian built vans, he goes to some length describing how the Australian factory thought that they were clever extending the sedan floor. Luckily he's put the
article online:
Although the van’s wheelbase was 10cm longer than the saloon, engineers at Zetland devised a clever extension to lengthen the standard saloon floorpan. This meant that only the panels and parts from the B-pillar back, and above the floorpan, needed to be imported from the UK. These were the roof, sides, cargo floor, outer sills, rear beaver panel, rear doors and hinges, roof vent, taillights, fuel filler recess, fuel tank and numerous smaller items. The rest of the van, including all front panels, grille, bonnet, floorpan, seats, trim, windows and the doors would be made locally and in common with the Morris 850 saloon.
Former Product Development Manager Peter Davis, who was responsible for drawing up the Knock Down Allocation Schedules (lists of parts needed for CKD) said that the earliest Vans assembled in Australia used complete bodies brought from the UK, and that it was not until early 1965, that the Australian floorpans were used. Peter Davis recalls a later trip to the UK; “I went to Longbridge, to Cowley, and Castle Bromwich – where they were building the Mini vans and utes, and that’s where I told them about the floors. They asked me why we didn’t order the floors and I said because we use the saloon floor. They said it couldn’t be done because they were a different length, and I told them we made up and fitted these extensions. They said they had completely re-tooled for the van, from the grille to the back doors. You can imagine the extra cost in doing that.”
Perhaps Peter Davis' memory has faded a little over time.
Tim
In the photo attached on the RHS only of the tunnel on the extended rear floor section there is a small tunnel feature formed into the metal leading to the underside of the main exhaust tunnel. (near the brown leaf!) Obviously put there for a reason by the factory, anyone know what it is there for? 
Watto won't be wrong!