Closing in favour of https://bugzilla.redhat.com/show_bug.cgi?id=2112384.
FTR has we chosen to go this path, the documentation adjustment would be like changing "Controller" to "Controller, Compute" in step 4.2.2 here https://access.redhat.com/documentation/en-us/red_hat_openstack_platform/16.1/html/scaling_deployments_with_compute_cells/assembly_creating-and-managing-the-cell-within-the-compute-service_creating-managing-cells