I see it as quite feasible that an attacker could insert a fob or organise for a fob to be inserted without also having opportunity to reboot the computer.

That fob could then compromise the system when the computer was rebooted. The Lenovo bios setting being discussed would prevent that.

BTW Can you clarify if you think the feature from Lenovo is a good or a bad thing given your claim that it's very easy to disable?