What does "Not independently verified" mean on a vendor profile?

It means exactly what it says: this site has not confirmed that item against an authoritative source, so it is not asserting it.

It is not a negative signal about the company. Regulatory status fields in particular start in this state by default, because approved, cleared, authorized, and certified are distinct terms that must be checked against the relevant regulatory record for a specific product, not carried over from a vendor’s own description.

Where verification is completed, the record shows what was verified and when.