Just a guess, but would "super-structure" (lat.
above structure) not simply refer to "decks" above the weather deck? As per the example (Level 01 etc).
Shallow curving might also be necessary in the problematic hull support pylon: a straight corridor running down the middle would divide the space into uselessly small halves, but a corridor curving along one side would leave maximally useful rooms on the other. Not that too many decks in the neck would have corridors - but Deck 12 just might.
There's just no room (or point) in having 8' wide corridors in the neck pylon - the neck is only 16' at it's widest, even before allowance for hull thickness is taken into account. The corridor (S-shaped or not) would obscure most of the floorspace - might as well widen it to accomodate the whole deck!