You've probably seen a variation of this before, sometimes called a Frankenstein squat. Both use what's basically a "front squat without hands" position. Here's Christian Thibaudeau doing the heavy bottom-up version:
The paused zombie squat, starting from the top, is one of the best drills to teach an efficient movement pattern when front squatting. It's a fantastic "self-limiting" exercise. If your form turns to shit, there's no way you'll be able to continue without the bar falling to the floor.
Paused Zombie Squat
Everything has to fire in a coordinated and efficient manner or the bar will roll off your shoulders. The pause at the bottom forces you to stay tight, ensures that your movement is locked in, and builds confidence.
This variation can also be used as a tool for teaching a good bar position and upright torso during the front squat. Upper-back rounding is a very common front squat (and goblet squat) mistake, but this is eliminated with the paused zombie squat.