Currently, when you deploy a template with an upstream, it stays under the previous owner and doesn't require a fork with the new eject feature. However, if you're creating a project from scratch or disconnect/eject a template upstream, you can only connect one you own.

For many reasons, mostly maintaining an up-to-date and stable version while not cluttering your repo forks, the ability to connect a repo you don't own to the upstream would be amazing.