With the multitude of assistance exercises one can use to improve their Olympic lifts, the more specific the assistance movement (i.e., the more similar it is to the classical lift) the greater the carryover. In regards to squatting, one should strive to use the same range-of-motion and dynamics used in the competition lifts. In other words: don’t half-ass your depth unless you’ve got a good reason to (e.g., caution with an existing injury, intentionally heavy partials, etc.). While I can’t state this as a fact, I’m pretty sure Pisarenko dies a little bit on the inside every time someone uses a medicine ball to gauge the depth of their front squats. Please be considerate of this legendary athlete.
For an Olympic-style weightlifter, the squat is the king of assistance exercises. But at the end of the day, it’s just that – an assistance exercise. Don’t get me wrong, an Olympic lifter should strive to become an exemplary squatter, but not at the expense of padding one’s ego using big weights with poor range-of-motion.