Earlier quoted context omitted.
Sounds like a Chromium bug, not a Debian bug--it's an insidious way to keep Google search as the default.
Reporting that there is a policy is no bug, but maybe there should be a way to signify that it's customized by your software vendor (i.e. signed and keys are compiled in) and that it just sets the default search engine. Chromium does change the message to "This device is managed by " if attached to Chrome Enterprise.
Moreover, defaulting to Google is also a policy.