No, motion blur is not caused by that. Motion blur might be added intentionally to hide non-smooth movement with low framerates but that is uncommon outside of games or pre-rendered content (movies).
And for a 120 Hz display (or even higher framerates) the jump between frames is small anyway that any reasonable scroll speeds will appear as smooth without the need for motion blur.
If you are seening motion blur on a high-framerate display then either it was already there in the source content, intentionally added by the application, or you display has a crappy pixel response time. It's not an inherent problem with high-refresh displays.
And for a 120 Hz display (or even higher framerates) the jump between frames is small anyway that any reasonable scroll speeds will appear as smooth without the need for motion blur.
If you are seening motion blur on a high-framerate display then either it was already there in the source content, intentionally added by the application, or you display has a crappy pixel response time. It's not an inherent problem with high-refresh displays.