Right.
Means, if the bus turns about 180 degrees, and the passenger still looks straight ahead(within the bus), the passenger doesn't face anymore north in world coordinates, but south.

While the 'passengers' of the sphere - vec_for_vertex and vec_for_normal - keep their values after the turning of the sphere, what is relatively to the sphere absolutely okay, but it is not consistent in world coordinates, because their world coordinates changed.

http://www.puppenheim.org/
http://www.wuerfels-welt.de
Old Game Tutorial: http://www.puppenheim.org/MITutorial.zip
Free Game Editor: http://puppenheim.org/AlienalsWeihnachtsmann.zip
http://www.puppenheim.org/blender_starting_main_settings.txt