Steps to reproduce: Follow the steps below to reproduce the issue.
What I noticed: There is a "Finishing set up..." notice at the top right of the screen, with the rest of the area blank.

What I expect: A notice stating that this site is not owned by the WordPress.com user.
This cannot be reproduced anymore, if a site that is not owned by the customers is added to the url, the sitepicker will be displayed. I think we can close this.
Most helpful comment
This cannot be reproduced anymore, if a site that is not owned by the customers is added to the url, the sitepicker will be displayed. I think we can close this.