Can you describe how Signal leaks your phone number and what capabilities and adversary needs to get it? (I know the answer, I am asking rhetorically, because I don’t think that someone who knows the answer would make that case.)
An adversary could compromise the signal server and observe how messages are routed. Applying pressure or coercion to achieve this is well within the capabilities and willingness of state-level adversaries. An adversary could also compromise the person you are communicating with, not to mention cases where you don't want to leak your physical identity to a someone you are messaging.
