My 2018 model 3 P with FSD had tesla vision pushed to it (without me requesting FSD beta) and as I have said in a couple of threads I have been trying for close to 2 years now to get tesla to put be back on "regular" FSD instead of FSD beta. I dont use autopark, but my parking sensors definitely seem less accurate.
I havent seen anything that guarantees that all cars with sensors will never run on TeslaVision, so if I was buying, and "no teslavision" was a must have feature, I wouldnt buy a tesla model 3 or Y (any of them).
Note that I still like my 3 (and my wifes Y), but I also dont believe every car is for every person, and if the first stated goal is "Im buying a used one because I dont want XXXXX" on these cars that firmware update all the time, I would say "dont buy it expecting it to stay how it is, since the stated goal is this other thing"
Shrug, at the end of the day its OPs money.