Why the number is about the mouse
Dragging a finger across a button makes the contact skip, and each skip is a separate switch closure. The browser receives them as ordinary clicks and this page counts them, which is how drag clicking produces 1,200 CPM and more when a trained hand on the same button reaches maybe 950.
Whether it works at all depends on the switch and the shell. Many mice never chatter no matter how you drag, and no technique will change that — so a run with no bursts is usually a fact about your hardware rather than your grip.