You can factory reset it, but not really. On first boot, the phone requires a network connection; you can’t skip setting up wifi if there is no cellular internet available. And it will ask you to authenticate the google account it expect before even starting the “real” setup process. As a matter of fact, once you authenticate with google, it does start again, ask again for wifi and will not have the account setup at all, as you would expect after a factory reset.

So, while you can “factory reset”, the phone still needs the previously registered google account to start. There’s probably some phone that gives more leniency, but I was not able to circumvent that using adb (the device being locked, and impossible to unlock without accessing the menu, impossible to access without starting in the first place…)