Originally Posted by NZedPred
This link has some explanation of bootloader locking and unlocking, and the security side of things (scroll down to near the bottom).
It doesn't really do much to explain in detail why the relock requires a factory reset, but essentially it's to ensure that there is nothing in the phone that could have been compromised. When the bootloader is locked, certain app developers want to be sure that the device is secure. Any leftover remnants from a rooted device are a potential security issue.
The link does not say that the device will be reset and the user data will be wiped upon relocking the bootloader. it just says that it will provide the same protection after locking the device upon installing any custom rom and then unlocking it again.
Who gets to say what is "compromised"? The OS provider Google or the device manufacturer or the users who have paid for the software and the hardware of the device and owns it?
if those certain armatures app developers can't write their own stuff secured enough and actually depend on OS to provide them protection at the expense of crappy user experience with limited innovation and hijacked creativity, then that's their problem. An owner of the device should be able to install any OS even that they may have build in their basement or any jack **** they want...or live with the crap that they got from OEM . Just like Windows on any computer can let you do what ever you want to do as an administrator...whichever sites and application you want to access and run. Why is Android (linux) so overtly protective about giving root access to its users?
Anyway, relocking the bootloader will wipe the device again even if you have not installed anything customized even immediately right after unlocking that has already wiped the device...I just don't understand or like the logic behind resetting the whole device upon relocking the bootloader...is Google afraid of people coming after them for security issues on their customized/rooted device? hmmm... if that was the case with Windows, Microsoft would've been bankrupted long ago.
sorry about the above rant, I just woke up after 18 years in coma and I find the mobile device industry still in its infancy... or maybe I just have lost my mind.