With ansible-galaxy, multiple collections can be downloaded in bulk using a requirements file ('ansible-galaxy collection download -r requirements.yml').  However, publishing collection tarballs must be done individually, using a requirements file isn't allowed.

For disconnected or airgapped environments, it would be useful if 'ansible-galaxy collection publish -r requirements.yml' worked, since collections can't be synced into a private automation hub from the internet-facing Automation Hub.