The current documentation as of today
https://gnupg.org/documentation/manuals/gnupg/kbxutil.html

still says that

(4) Well, OpenPGP keys are not implemented, gpg still used the keyring file pubring.gpg.

This has changed, at least since 2.2.
Would be nice to update the example output as well, e.g. to

Total number of blobs:       33
               header:        1
                empty:        0
              openpgp:       29
                 x509:        3
          non flagged:       32
       secret flagged:        0
    ephemeral flagged:        0

(an output created with gpg (GnuPG) 2.2.13)

An additional plus would be to list the GnuPG versions when this was released with and switched to default.