A person who can squat to full depth will always be able to squat to partial depth, but a person who cannot squat to full depth may find themself in trouble if they ever reach an inadvertent depth.
Why not prepare for it all and train yourself to own every inch of range of motion that is available, to unlock all of the potential of your squat?
If you ask me, some trainees need to squat deep.
If you ask me, every trainee should (at least) try to squat deep.
A few examples of ones who need to squat deep are powerlifters, weightlifters, and sport athletes. A powerlifter needs to reach a certain amount of depth to be awarded a successful squat in competition. A weightlifter needs to be proficient at squatting as low as possible in order to receive snatches and cleans at lower heights. A sport athlete is destined to wind up in various crouched positions that they must recover from and get out of quickly in order to remain a participant during their games.
Everyone else should be attempting to squat as deep as they can.
To me, “as deep as they can” means as far down as they can go while maintaining form and balance. It does not mean as far down as they are comfortable going.
Depth: Unnatural vs. Unfamiliar
If as you venture to greater squat depth, your heels peel off the ground, your knees sandwich together, and/or your back begins to take the shape of a waxing crescent 🌙, you may be trying to go too deep, for now at least.
If as you journey to greater squat depth, you stop at any point because you are unsure you will be able to get back up, you could probably go deeper, you just have not tried enough of it yet.
The former is an example of someone who is trying to force a range of motion that is unnatural, and an argument could be made that attempting to go that deep should be avoided in order to prevent injury.
The latter is an example of someone who is reluctant to squat deeper because of an unfamiliar range of motion, which is just uncharted territory. This, in effect, presents unexplored room to build more strength, mobility, and coordination than their current squat depth. This should be considered encouraging!
More depth: Making Unfamiliar, Familiar
If you aspire to develop a deeper squat, you will need to practice it regularly.
Obviously, you will have more trust in yourself squatting lighter weights to greater depths than you will heavier ones, so take full advantage of building confidence on your lighter sets. Make a concerted effort to travel further down than you normally do as you are warming up and working up in weights.
If you form the habit of squatting lower during your lighter sets, it will begin to translate to your heavier sets over time.
Once you are equipped with the ability to squat to full depth, it does not mean you need to get there with every set, but there will be a higher probability that you bail yourself out if ever the weight pushes you lower than you want to go.
To sum up, do not force more range of motion if your body is not ready for it, but do reflect on the reason you cut your depth at a specific point if there is still room to go deeper. If it is not due to pain or a mobility restriction, consider testing out a deeper squat.
Be patient, go about it slowly, and drill it with consistency.