The beam leaves a "ghost trail." This creates a wall of light that wipes away the mental image of the feed you were just looking at.
Saccadic Masking: The brain cuts visual processing during rapid eye movement. By forcing continuous tracking, we interrupt the pattern recognition loop that craves the next dopamine hit from a feed, effectively "wiping" visual short-term memory.
Scrolling makes you anxious because you are hunting for information. Tracking the beam is predictable and calming.
Parasympathetic Activation: The predictability of the sine-wave motion combined with Pink Noise (1/f noise) lowers Beta wave activity and induces Alpha/Theta states, effectively turning off the "Fight or Flight" search mechanism triggered by social algorithms.