The big mistake is mistaking box squats for regular squats. They are, and should be different, provide a much more focused stimulus to the posterior chain.
Doing them today, after a long absence of them in my program, revealed I can no longer sit back into them the way I used to, and that my posterior chain is weaker.
Neither which was unexpected.
For an olympic lifter, expect box squats to NOT help you where an improvement in the front squat, or even the back squat to help you, but probably in the pull.