Taking the thinkpad apart is part of flashing the bios, which usually is just clipping an SOIC8 clip to the bios chip and using CH341a SPI usb programmer to flash it. I did the same to my thinkpad x220 to flash it with coreboot.
Thanks for that. I was still wondering why the flashing couldn't be achieved on a running system as-per the usual method of updating the proprietary manufacturer's BIOS. I found this key quote on the Coreboot web site:
There are various protection schemes that make it impossible to modify or replace a firmware from a running system. coreboot allows to disable these mechanisms, making it possible to overwrite (or update) the firmware from a running system.
Usually you must use the external method once to install a retrofitted coreboot and then you can use the internal method for future updates.