Hello, Red Hat Capsule and Katello Content Proxy are essentially the same thing but there is a big difference in docs. In the new (4.0) documentation, foreman-maintain tool (which is the Red Hat supported way of installing/upgrading packages or deployments) is used while the old Katello docs does show performing direct commands (which are executed by the tool anyway). Unfortunately, foreman-maintain and/or the new documentation hasn’t been adopted for Katello 4.0 yet, this is still a bit rough and we need to either improve this or revert back to the non-foreman-maintain upgrade instructions.
I think that goferd is no longer available and these commands are not necessary but I am not really sure this needs to be confirmed. All and all, it is definitely not the best experience for you, this is very much fresh content as we are migrating Katello docs, if you can wait for confirmation from @ehelms or @ekohl or other experts from the installer team, then just wait. If you need to proceeed now, then falling back to the original docs should work.