I actually know someone who thought that the ram air in actually provided the cabin air pressure.
BOAC,
never thought it sir, and least of all, said it ... but the thing I know for sure is that every kind of source bringing air into the cabin and not allowed to exit, does increase the pressure in it ... and, that's called Pressurization. If the RAM air allows air to freely enter the cabin, and at a certain point is not allowed to exit, it also contributes to a pressure build-up, obviously weaker and slower (the so called pre-pressurization).
Bio161,
as far as I know the "rule" applies for every aircraft on earth, and not just the bus. To minimize the hoop stress into the fuselage, only a small differential pressure is allowed fot takeoffs and no residual differential pressure's allowed for landings. That's what I studied ...