We use it and we set the common-name by hostname by default (https://github.com/Katello/katello-misc/pull/17/files#L2R316), we just allow also setting the common name different from the hostname.

The hostname needs to be set just becaues ths katello-ssl-tool organizes the certificates into directory based on the host name (so that all the certs for given hostname are on one place), which is quite useful when distributing the certs after generation.