Since the resource by stack has not been created before deploying overcloud, it is assumed that `--config-download-only` cannot be executed at this time. Reported by: rhn-support-tasakura https://access.redhat.com/documentation/en-us/red_hat_openstack_platform/17.0/html/director_installation_and_usage/assembly_provisioning-and-deploying-your-overcloud#annotations:1e57a321-153e-4a87-b3fa-aa3d64d3c9bf
In step 2 from https://access.redhat.com/documentation/en-us/red_hat_openstack_platform/17.0/html-single/director_installation_and_usage/index#proc_validating-your-overcloud-configuration_ironic_provisioning, replace --config-download-only with --stack-only. Also remove the wording "plan". As there is no plan in 17. I would just call it "stack".
Regarding validations aspect. Always run validations with explicitly defined inventory file, if at all possible. Otherwise you get the 'No host matched' error, because the runtime has no idea how to reach target machines. The reasons col may be too large to see all results at once. In that case I would recommend changing output format, it is one of the CLI params, and piping the result into a file. After that you can use UUIDs of individual validations to inspect their results in detail.
Updated content available on the Customer Portal: https://access.redhat.com/documentation/en-us/red_hat_openstack_platform/17.0/html/director_installation_and_usage/assembly_provisioning-and-deploying-your-overcloud#proc_validating-your-overcloud-configuration_ironic_provisioning