The action "Save Secret Team Key" is also offered if the secret key only resides on a smart card, not on disk.
If the key is not on disk, too, the action should be greyed out, same as "Backup Secret Keys".

Btw, "Save Secret Team Key" does in this case create a file named as expected for a team key (Berta_Boss_0x458612006D8E6F0D_SECRET_TEAM_KEY_ENCRYPT.asc) . Importing it in another keyring results in import of only the public key only, though there seems to be some information included that it should be a secret key:

gpg: key 458612006D8E6F0D: public key "Berta Boss <Berta.Boss@demo.gnupg.com>" imported
gpg: To migrate 'secring.gpg', with each smartcard, run: gpg --card-status
gpg: key 458612006D8E6F0D: secret key imported
gpg: Total number processed: 1
gpg:               imported: 1
gpg:       secret keys read: 1
gpg: marginals needed: 3  completes needed: 1  trust model: pgp
gpg: depth: 0  valid:   1  signed:   1  trust: 0-, 0q, 0n, 0m, 0f, 1u
gpg: depth: 1  valid:   1  signed:   0  trust: 1-, 0q, 0n, 0m, 0f, 0u