Looks like CrossFit HQ wants people to learn proper Handstand Push ups (i.e. non kipping).
For this they made a video series with top gymnast Dave Durante (part 1 here).
I used to do this particular exercise, the Jackknife (or Pike Up) with physio ball, a lot when I trained for my Press to Handstand.
It really helps with with getting the compression right and well as with building shoulder endurance. Also it is a very nice core/abs exercise as well, ideal for a finisher once you get the movement down.
Start with the way they do it in the video and later increase range of motion (by doing it on blocks).
For more excellent Handstand tips check out Dusty Hyland’s Handstand series or check out the ATG “Handstand” Category.
Handstand Push Up Progression with Physio Ball is a post by Gregor from All Things Gym.