You're right, it's a jump with the bar, where your feet might or might not leave the ground.
Not to contradict that at all, the jumping description can be detrimental, like if someone thinks of it too much as jumping, they might add a "donkey kick" just to get their feet off the ground.
Back to the OP, as misspelledgeoff already said, as the weight increases, you'll eventually need to quarter squat to catch the bar. Power is moving a heavy object fast, and power is at a maximum in the PC when it's the heaviest weight you can catch somewhere in the quarter squat range. When the weight is light enough that you catch it standing, you lose the heavy (high force) element of power. When the weight is so heavy that you have to full squat to catch it, you lose the speed element of power. In the middle is the sweet spot.
This study on hang power cleans has a plot of power vs %1RM. Power was at a max at 80% of 1RM, though the error bars are so big that it's possible the sweet spot is pretty big, too, and I didn't read how they determined 1RM.
The PC always seemed the most nebulous to me as far as when to switch from 10 lb jumps to 5 lb jumps, because it's a judgment call whether you missed a lift. I imagine the answer is in the book, and I just need to re-read that section, or use the search function.