Earlier quoted context omitted.
Read again. It does. The boot ROM fails to verify the bootloaders (XBL) signature for some reason.
Read what again? If the flash bootloader is failing to verify, I should be able to send a new one over the USB port, even if that requires wiping the device for security purposes. Defending against an evil maid attack doesn't explain why I can't do that.
More details: https://blog.quarkslab.com/analysis-of-qualcomm-secure-boot-...