I'll try to keep this brief. Please ask if something more is needed.

As a user using a DNS-enabled (for example) smart-proxy in a particular domain and subnet, the using-components are not made aware of changes that happen later to the smart-proxy.

To describe more fully:

After disabling a smart-proxy feature, Foreman does not automatically become aware of it. This may not be an issue that you really want to fix at this time. Please continue reading, it isn't really the main issue.

To work around, using the UI, a person can "edit" the smart proxy and save the form without changes. This would seem to be a noop, but does cause smart-proxy feature rediscovery. With Foreman now aware that a feature is gone, it still DOES NOT disable it in the places that had already been configured (domains, subnets). To work around, it is necessary for the user to also re-save those forms (without apparent changes) before foreman will actually stop trying to use that smart proxy feature during a host's lifecycle (probably results in "404" being reported by the task runner). That may be something worth fixing? If so, one solution is to take an appropriate cleanup action after smart-proxy feature rediscovery.