It's not clear to me what your point is. Are you saying that my suggestion that the article should have addressed a different (similar) hypothetical is at odds with your imagination and the physical structure of bone?
It's an answer to your question "why haven't organisms evolved which use iron in their skeletons". The physical structure of bone would not be improved by incorporating more iron, so there's no reason for evolution to move in that direction.
That's not my question… that's the question I would have preferred the article addressed. I already gave an answer to the question in my original comment.
Also, the 'explanation' begs the question, why wouldn't we see a bone replacement evolve that's suited for iron reinforcement? Your clarificiation is a small step down the 'whys', but saying "because bones have evolved to use calcium" is tautological.
