"The stated goal is stopping robocalls."

this will do nothing to stop robocalls.

robocalls do not originate from private individual subscriber accounts.

there is some reason why commercial interests, are allowed to have ANI trunking and SS7 access even though it is used to spam spoof and fish, as a mainstay, despite the economic losses resulting fromthese crimes.

lets put it another way..

we cant stop robocalls and coldcall scams unless we have PII of all individual subscribers, and let commercial interests have anonymous unbiased access, as if they are legitimate. anybody wanna buy that?

Attestation is already in place from STIR/SHAKEN. You can test your carrier here: https://clearlyip.com/services/attestation-service/

The FCC’s database of compliance is here: https://fccprod.servicenowservices.com/rmd?id=rmd_listings

This is the next step in KYC.