Error generating subkey in gpg's batch mode using curve brainpoolP512r1

[sgh at erghfe.com]

Hi!
Using the curve brainpoolP512r1 to generate subkeys for signing and verification for a key reports an error, using the following command:

printf "$pass" | \
gpg --batch --pinentry-mode=loopback --passphrase-fd 0 \
    --quick-add-key $fpr brainpoolP512r1 sign 0

Output:
gpg: Key generation failed: Wrong key usage

The brainpoolP512r1 curve supports signing and encryption via https://wiki.gnupg.org/ECC. In the above command, subkeys can be generated normally when usage is encr, but using sign and auth will prompt the “gpg: Key generation failed: Wrong key usage”.

Subkeys with signatures and authentication can be added normally through the --full-generate-key interaction mode.

Is this an incorrect Gnupg configuration or a bug?