When a trust anchor does verification and issue you the certificate, you get a PEM file, their connection to the process is done. Yes they know who you are but can't track what you do with the certificate after they issue it to you.
On the other hand if you were to use that certificate to commit a crime, the signature will provide access to the trust chain, thus law enforcement could use it to find you by reaching out to the issuer. This is a feature not a bug, it combines privacy and accountability, no different from conventional non-digital world expectations.
The use of receiver id, happens after you have the certificate, the issuer is not involved. The receiver id is for the benefit of the receivers of signatures from your certificate, it allows them establish a sticky anonymous cryptographic identity for you without knowing who you are, this is a way again to have privacy while having accountability. This demo touches on the approach: https://www.youtube.com/watch?v=92gu4mxHmTY
Reach me via my profile if you're interested in knowing more.