It looks bulky and I think I would be bothered by the spring mechanism right behind the knee when in a deep squat. I think the little guys/girls have enough issues with gear size without adding more stuff for them to move around in.
I would be curious to see the range of motion in those. It looks like they might get to 90 degrees and maybe a little more but I know when my DD is in a deep squat between pitches as she is giving the signals, her butt is on her ankles. I also don't really like the normal knee savers because it tends to make girls lazy and sit back on their heels.
I honestly don't think these would be beneficial at all. I could be proven wrong, but girls aren't just "jumping" up from the squat. They're going down into full, entire body, blocking maneuvers, and jumping side to side. It's not just a straight up and down squat. Plus, when a catcher is in the receiving position they should actually be fairly relaxed.