Cracking PSA 9 and Resubmitting to PSA

[nocontest]

Apologies if there is a thread already discussing this as I could not find it. Received a big submission back the other day with a fair share of 9s. To me, I can't really figure out the difference between the ones that got 9s vs 10s. And have heard plenty of people say over the years "PSA 9 but looks like a PSA 10!" or "Identical to PSA 10". As grading is subjective and there exists the possibility of pop control I was wondering if anyone has ever taken all there PSA 9s, uncracked, and resubmitted. Be curious to know if some came back 10s and would the % would be. Thanks