I used a similar camera a couple of years ago for work and spent more time after-hours trying all sorts of stuff. (At $5k a week to rent, why not)
Cool was hitting a water balloon with a dart and watching the skin peal away a leave a ball of water hanging there or a firecracker go off in slo mo
What was missing in the attached explanation was that the re-collapse of the hole formed by the water droplet provides the pinch mechanism and itself can create a jet of water coming back up larger than the original droplet, depending on the initial speed of the droplet. Note that the syringe was close to the surface. Rain drops would impact with much higher velocities and a different phenomena results.