Chromium OS source released

What you've quoted is a single bullet point. The actual description of
Verified Boot states:

"It is important to note that restraining the boot path to only Chromium-
is run that is not provided for or maintained by upstream, that the user
will have the option to immediately reset the device to a known-good state.
"

Not being able to run third party code _without knowing it_ seems a good
thing.