No, I think you're wrong. If you put an Iowa up against the Yamato, the Iowa would have come off the champ. The Yamato was poorly constructed, it was slow, it had difficulties in seakeeping and was not an efficient use of resources. It was, in effect, merely a barge made to drag along big guns which never did any serious harm to anyone. It was a testament to Japanese pride and not so much a viable weapon of war.
That guy's contention was that because the biggest battleship in the world was vulnerable, all of them were. And perhaps they were, but to varying degrees. That vulnerability was subject to many different variables such as the proficiency of damage control parties, damage control equipment, spacing of machinery, armor belt, quality of steel, reserve bouyancy, etc.
The Yamato was not so much a batllehsip as a monument and that's why it was a non-factor in the war.
The Yamato's guns though bigger had a much slower rate of fire. The Iowa's guns had near equal armor penetration power, better radar control and could unleash two rounds per minute as opposed to one round every two minutes.
Yamato at 6 knots slower could not manuever as fast and is easier to hit.
The Yamato which was flagship of the Combined Fleet for most of the war was referred to "as a floating hotel for idle inept admirals" by many Japanese line officers during the war.
I grant all your points (regarding superiority of Iowas over Yamatos); minor quibbles over relative technical minutia don't change the vulnerability of tube-based naval firepower, compared to the standoff capability of a carrier.