Ok, the thing you have to understand is that a squat clean and a power clean are two different lift. In the power clean you are trying to create as much upward movement of the barbell as possible, whereas in the squat clean the goal is to pull the bar just high enough to receive it in the low position.
The thing is that if you do a squat clean you can't pull as high as you can and then squat down under it, the bar will just travel too high and crash on you.
But you can't "underpull" either otherwise you will lack power and the bar will be too far forward.
You still need to fully extend but learn to give it just enough power to catch it in the low squat position.
The best weightlifters aren't those who pull the highest, it's those who are the fastest and most precise moving under the bar.
Here is a drill sequence to learn to do that.
DRILL 1 - DROP CLEAN
Here simply go up on your toes and shrug your traps then from there move under the barbell as fast as possible, DO NOT do a pull once you reach the full extension, just move under. TIP: when going under do not think about squatting down, think about punching the hips back as fast as possible. The position of this drill is how high you need to pull a bar to clean it.
DRILL 2 - TALL CLEAN
Same as drill 1 but you do not pause at the top of the extension. Do not give yourself a swing to lift the bar, just do the body extension.
DRILL 3 - HIP CONTACT CLEAN
Same as above but you create some separation between the hips and bar and bring them together rapidly, as soon as you feel the contact it's the signal to extend.
DRILL 4 - MEDLEY LEADING TO HANG CLEAN
Same as above but the last rep is a hang clean. Lower the bar toward the knees and stand up, when the bar contacts the hips/upper thigh it's the signal to extend.
IMPORTANT: you don't jump up! You extend your body up and when you reach full extension you quickly punch the hips back to go under. If the feet move (and hit the floor) it's because of the super fast movement of the hips NOT jumping up.
NOTE that both guys can clean in the mid-300 and they can still do a full extension with baby weights without overpulling. That's what you need to be good at squat cleans: being able to pull every weight seemingly the exact same way while always bringing it directly to the shoulders, not having the bar launched in the air and crashing down on your from 1 foot above.