OK, then if you are going to make this change, change the tooltip for the Iron Working tech that still says "reveals iron," and please offer a rationalization in the Civilopedia entry as to why bronze working somehow reveals iron. Since there is neither a copper resource nor a bronze one, you could even change the name of the Bronze Working tech to make more sense in revealing iron.
Otherwise, I think you should instead either reduce the science cost to get to iron-revealing Iron Working, or make Horsemen require iron or something else to reduce their numbers (maybe two horses for one unit).
Otherwise, I think you should instead either reduce the science cost to get to iron-revealing Iron Working, or make Horsemen require iron or something else to reduce their numbers (maybe two horses for one unit).