This is not about pixel response time. This is for the same image to be held over the whole time interval of the frame, instead of just momentarily, meaning that movements from one frame to the next suddenly “jump” at the interval boundaries, instead of being smoothly interpolated by the eye/brain between momentary flashes like with CRT. Even with instant pixel response, sample-and-hold displays inherently produce motion blur. This is why mitigation techniques like black frame insertion, backlight strobing and scanning backlights exist.
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.
