Considering the researchers who actually disabled IME require physical access to the machine[1], Purism's claim that they can do it to previously sold devices with only a software update[2] stinks of BS to me.
[1] https://wiki.gentoo.org/wiki/Sakaki%27s_EFI_Install_Guide/Di...
[2] https://puri.sm/posts/purism-librem-laptops-completely-disab...