And water has oxygen in it, but I wouldn't go trying to breathe it. D:
The reason this has happened is, presumably, these items used to use iron on the. However, the Japanese name is just (Heavy) Metal Jig. So when the material was changed, the name did not, as metal is metal. As there was no name change on the Japanese side, the localisers would not have noted anything as having changed. And here we are!

anyway ya make it steel basically