Why am I seeing output on `gpg --export-secret-key` when my secrets are on my smartcard?

I have a Yubikey with my GPG private keys on it, and public keys in my gpg keyring. I made sure that private keys are not present on my system by running gpg --export-secret-key -a which returned nothing but gpg --export -a printed my public key. Next after setting up my ` for signing I noticed that I still get a private key printed on --export-secret-key` after unlocking my card and using it to sign something. This baffled me because I wasn't expecting anything to be printed on --export-secret-key so I am curious what this key is? To be sure I have also tried deleting this private key --delete-secret-keys but using the smartcard again, populates the private key for this ``.