interesting observation. When I had my tyres changed they inflated to recommended pressure for an unloaded transporter, 36psi, as that is what the data sheet said.
Naturally before I wheeled away I asked them to inflate all 4 to 45 psi, the loaded weight according to the door plate. "how often is it fully loaded" I was asked, rather scornfully.
Now, given the weight of the Haldex, the camping furniture, kitchen and fridge, the generally half full water tank, the permanently filled clothes drawers and cupboards plus all cooking stuff, I felt quite secure in saying "more or less always". I thought the tyre man was going to go nuts, but finally resolved to give me his "Stupid woman driver" look.