Some sites rely on the first touchmove event as an indicator that a tap is no longer possible and scrolling is about to begin. Eg. to clear a depressed state on a button from JS, or to drive custom scrolling without triggering accidentally on tap.

I see that Edge sends pointermove events during a tap when there is a little wiggle. This must mean that pointer-event-driven carousels would sometimes wiggle when tapped. Today developers could only approximate a solution by doing their own slop suppression using some distance heuristic.

Depending on the outcome of #123, we could perhaps define an event that fires when :active state is cleared (or a way to query whether an element is currently :active that's better that getComputedStyle).