As exposed in current discussions, it is only that the fleur-de-lis achieved more popularity in France and not that it necessarily has to do only with that nation.
In the case of Spanish sword smiths, as in this case, you may relate such symbol with the heraldry of Spain, where the arms of the Bourbons figure in the Spanish flag.
Concerning the for-the-lis symbol in Juan Martinez blades, there is old solid evidence that he (also) used this mark. Whether it was his personal symbol, a quality seal or the mark of his status of ESPADERO DEL REY, a honorific title for smiths granted by the crown, is subject of discussion held in THIS THREAD
, namely in post #3.