Dear craig_j ,
The mouse scroll wheel does not tell ArchiCAD anything, however ArchiCAD can poll it to determine what use it wants to make of it. When you are running Revit, Revit can poll it. ArchiCAD may or may not make the same use of what it polls as Revit does. It completely depends on what the developers of ArhiCAD have decided to do with the signals it polls from the the scroll wheel. The same would apply to input from any and all input devices. It is completely up to the design of the application. If you want to know why you are experiencing a certain behavior in ArchiCAD, you would need to contact the ArchiCAD developers. If you want to know why you are experiencing a different behavior in Revit, you would need to contact the Revit developers. The behaviors are all directly dependant upon how the application was designed, not by input devices.
The more things change, the more they remain the same. ; ^ )