The pinch gesture is always interested in the touch session. When a new touch is added, the distance between all of the touches is registered in order to check for distance changes equating to a pinch gesture.

If a touch cancels, the pinch remains interested (even if there's only one touch left, because a second touch may appear again), but updates its internal variable for tracking for pinch movements.

If a touch ends, the pinch remains interested (even if there's only one touch left, because a second touch may appear again), but updates its internal variable for tracking for pinch movements.

The pinch is only interested in more than one touch moving. If there are multiple touches moving and the distance between the touches has changed then a pinchStart event will fire. If the touches keep expanding or contracting, the pinch event will repeatedly fire. Finally, if the touch distance stops changing and enough time passes (value of pinchDelay), the pinchEnd event will fire.

Therefore, it's possible for a pinch gesture to start and end more than once in a single touch session. For example, a person may touch two fingers down, expand them to zoom in (pinchStart and multiple pinch events fire) and then if they stop or move their fingers in one direction in tandem to scroll content (pinchEnd event fires after pinchDelay exceeded). If the person then starts expanding their fingers again without lifting them, a new set of pinch events will fire.