DO NOT BUY FROM VERIZON if you want to unlock your bootloader. This also applies to Rogers in Canada and EE in the UK. They will force your bootloader to be locked for life, creating more e-waste. This sounds sketchy, needing to keep a phone on the same Android install to be unlocked. I would not advise you to buy this device, because I’ve never heard of this phenomenon. I can’t say for sure, but it sounds like the seller may have installed malicious apps that will be removed if the device is factory reset, so the sellers wants you to not reset it in order to keep the malicious app on the system. This is just a guess, and this could be a new scummy thing created by carriers to keep their customers attached to them.