Signal has access to more data than they would like you to believe. Each account at Signal is identified by a phone number or an UUID. This account also contains a [list of devices](https://github.com/signalapp/Signal-Server/blob/c21eb6aa5098...). Each of the devices has some uinteresting metadata assigned to it, but more importantly it links to a specific Android or iOS device through the [push token](https://github.com/signalapp/Signal-Server/blob/c21eb6aa5098...). This gives the authorities a link to an account at Google or Apple which then of course contains much more data.