Stephen was the first to begin striking monies with his own initials on them and not those of the Byzantine Emperor. He was not attached to the empire in any way: neither by appointment nor by any other ties except heritage of his dukedom.
Stephen was the first to begin stamping his own initials on coins, bypassing the Byzantine Emperor's insignia. He had no official ties to the empire; he wasn't appointed or bound by any other connection besides his dukedom lineage.