The issue isn't that the console isn't working in admin-only mode. It's that a permanent redirect is issued for a temporary condition. The redirect from the console root URL should use a 302, not a 301, since the appropriate target depends on whether the server was started in admin-only mode.
The root URL of the admin console ( / ) does a permanent redirect (301) to the final target. Normally it's a redirect to /console/index.html. But if the server is started in admin-only mode then /console/index.html doesn't return a sensible error (Chrome reports that the connection to the server was lost). If a browser has cached the permanent redirect, it won't be clear why the console isn't working.
On the other hand if the server is started in domain-only mode and the browser caches the permanent redirect to /consoleerror/noConsoleForAdminModeError.html, then the browser will continue to load /consoleerror/noConsoleForAdminModeError.html even after the server is started without --admin-only.
A 301 redirect is inappropriate since "admin-only" isn't a permanent state.