Shouldn't Yamato's armor follow this layout? 270mm vs 165mm in game

Before this update dropped, i was studying Yamato’s design and armor, and now that it is here, i noticed that for some reason, the armor below the waterline is 165mm thick in game only, while it should be 270mm thick, i think.

Only the frontal/back side is modelled as 270mm, why is that?

Is that correct?

That diagram is wrong, and an average thickness was chosen.