Correct. Unlocking the bootloader trips a hardware flag that says "This bootloader has been unlocked", which voids the warranty. To date, nobody has been able t

Correct. Unlocking the bootloader trips a hardware flag that says "This bootloader has been unlocked", which voids the warranty. To date, nobody has been able to figure out how to un-trip that flag, though there was a brief window in which you could hack a custom ROM onto the device without unlocking it, but that was patched out with FRF91. Personally, I think that's pretty reasonable, since third-party firmwares could potentially do things to the hardware that'd cause damage, and it's silly for hardware makers to promise to fix things caused by user negligence.