Great article, Dan.
Just guessing here but removing the main passcode lets them turn on and off for testing (fairly obvious) and turning the TouchID off is necessary because that (and the secure enclave) is part of what gets replaced when you replace the front. If you replace a TouchID on your own, it won’t work because the iPhone doesn’t recognize the new TouchID’s serial number. That has to be “overwritten” inside the phone as well. Having the main passcode off and the TouchID off probably allows that to be overwritten. (or else you would just take a phone apart, replace the TouchID with one that has your prints in it to break into the phone)
Agreed though, creepy to hand over a totally unlocked phone. If I have to show up at the Apple store, I’m going to factory reset.