Dear Nick,
I believe that it is. The original author created a container that did not have the left and right side elements that are employed in the sections.
It could have the left and right elements, but in truth they are not needed as they would not contain any displayable information under any context. Unlike the sections that contain section number and editing icons. Adding side padding would only cause the number of grid boxes per row to decrease in smaller resolutions or be forced to reduce their size. Please experiment with resizing your browser with the format to see what I mean.
Therefore despite the aparent symetrical anomiliy, I believe the way it works currently is the way it should. After all, we don't want to assist the existence of the scroll of death for which the format is designed to hinder.
Cheers,
Gareth