Hold gestures merely denote "there are fingers on the touchpad but they are not moving". As touchpad touches are generally fully abstracted, a client cannot currently know when a user is interacting with the touchpad without moving - no motion events will be sent in this case.
The two use-cases here are:
Since hold gestures by definition do not have movement, there is no need for an "update" stage in the gesture.
Minimum todo list: