He states "The wheelchair had to be dismantled, passed through the lift window, and then reassembled before he was helped down the stairs."
I read that and assumed it was too big to fit through the door of the high lift vehicle, so it was taken apart and passed through the window, then assembled again.
The comparison with Cambodia doesn't sit right with me. If anything that is extremely degrading to be carried up the stairs like a child, in the rain. I'm not sure why he saw that as suitable assistance. That's worse than what happened at LHR, where there were trained,dedicated staff on hand to assist, albeit with a mishap. Cambodia may be a poor country, but it's airports should still meet international regulations with regards to disabled services. Admittedly he doesn't state which airport it was, it could have been a small airfield, but if it has scheduled services, especially international or wide body, then it should definitely not need a disabled passenger to be carried up stairs by the flight deck.