Earlier quoted context omitted.
where do chrome books fall on this spectrum?
Depends on whether you have bothered to open them up and remove the hardware-based firmware write protect. The process is highly device-dependent, and seems to be entirely undocumented for many Chromebooks and other ChromeOS devices. YMMV.
If there's devices missing, send a PR to that repo: https://chromium.googlesource.com/chromiumos/docs/+/master/R...