Sure, but that means that your phone number is linked to your identity even without Signal? There's no additional data that Signal links to it, other than that you're a Signal user and when you sent your last message.
Your previous question was "I'm not sure why you need to assume that it will be linked back to your real identity?"
If it's not possible to buy a phone without a strong attestation of identity, as is the general case in at least one country, then the identity relationship is baked in.
It's probably possible to buy a burner phone even in South Korea. But for those who are using their standard-issue phone with Signal, the problem most certainly exists.
And even in countries where there isn't some national phone-as-identifier policy, effectively most people's phone numbers tie them to their real-space identity even if there's no explicit personal data association[1], and in most cases, phone number, IMEI, AAID, and/or billing data (credit card payment authorisation) provide far greater assurance.
Point remains that 33 bits will identify any given person among the 8 billions now living, and a phone number itself, plus ancillary leakage (activity patterns, location) are an exceptionally poor basis for an anonymous or pseudonymous identifier.
<https://www.nfcw.com/2022/10/20/379863/south-korea-to-roll-o...>