See https://github.com/theforeman/puppet-foreman_proxy/blob/master/manifests/config.pp#L14. The rationale is that you can use dhcp, but not manage it using the standard modules. This will result in ```dhcp: true``` in ```settings.yml```, but not configure it with ```foreman_proxy::proxydhcp```. For example, you can use MS-DHCP, other puppet DHCP modules or even no puppet management at all.