This doesn't invalidate your point, but FYI, you can open your contact's info in the Signal app and see the number of linked devices they have. If someone is concerned enough about this, they could ask their contact to unlink all devices.
EDIT: I'm using a fork, which may be why I'm seeing it and others aren't. See below.
EDIT: I'm using a fork, which may be why I'm seeing it and others aren't. See below.