@komidore64 
it's nice to have, otherwise both options
--system-uuids
--system-ids
would show up in the help dialog making it confusing to the user. https://github.com/dustint-rh/katello/blob/0867b36b1e01fe6bdf2470a17038ec6edb2bcbab/app/controllers/katello/api/v2/host_collections_controller.rb#L64