I have seen that report about the engines being protected by iron, but obviously it would seem that the rest of the vessel was unprotected as such. My interpretation, based on such an account, would classify it as a wooden gunboat, and not as an ironclad.
Perhaps, as you state, when she was destroyed, she was in the process of being fully covered as an ironclad. Once again, this all boils down to a lack of proper documentation to confirm such an assumption.