How thoroughly are claims in copyright registration applications validated?
Let's consult The Compendium of U.S. Copyright Office Practices, Chapter 300
As a general rule, the Office will accept the applicant’s representation that the work was independently created by the author(s) named in the application
The U.S. Copyright Office generally will accept the facts stated in the application and other registration materials
Ordinarily, the Office will not conduct its own factual investigation to confirm the truth of the statements made in the application
As a general rule, the registration specialist will not search the U.S. Copyright Office’s records to determine if the work has been registered before
Likewise, the specialist generally will not compare the deposit copy(ies) with other works to determine whether the applicant is attempting to register a work that is substantially similar to another work of authorship
the existence of similar or identical works will not preclude a claim in a work that was independently created
More can be known about any questions the examiner may have had for the claimant. Applications, certificates of registration, and related correspondence are all publicly accessible upon request- and payment of a few hundred dollars in fees. Best Regards,Andriano