Invite-only, and no passwords. Enter the email your invitation was sent to and a one-time sign-in link comes back.
An address that was never invited gets an error rather than a link. This page does not disguise which is which.
After sign-in you go to whichever surface actually holds something for you. If that question cannot be answered you land in the workspace.
You see only your own room, and that is enforced by the database itself, not by this page and not by a promise.