Took it back to SC this morning, and had a nice conversation w/ the tech. I brought in my 0-60 log runs before and after the update (with zero delta), and the API values straight from the Tesla server (he was impressed, kept asking me how I got into the "mothership") showing my perf config as P3. He was still unsure what the problem was, but with the evidence I brought in he was convinced to look into it.
Picked up the car 4 hours later. He basically said, long story short, that I was right. They went through the process again, and now my perf config shows P1, and Vehicle status went from Standard to Uncorked. I did 0-60 log right after and time went down from 6 to 5 seconds. DONE.
Interestingly, he said there are two different uncorks for the 75D. One is the 1.1 second reduction in 0-60 time, and the other is .7 second reduction. I got the 1.1 second, I think it has to do w/ production date.
I can 100% confirm that for a 75D, the perf config should show P1 and vehicle status showing "uncorked," to know for sure uncorking procedure was performed correctly. Good to ask your SC to double check those settings since there seems to be a number of people like me who was not uncorked "correctly" the first time. Big thanks to everyone on the forum sharing all the essential info.