Why Brooklyn design Scheme B used a broken deck

Why did Brooklyn design Scheme B have a broken deck?

Dropping the deck continuation saved weight within the design's displacement constraints.

The answer is deliberately simple: removing the continuation of the deck saved weight. That saving mattered because the cruiser design had to fit a treaty displacement budget. The broken deck did not need a separate tactical explanation or imply a special operating doctrine. It is a compact example of how a visible change in sheer or deck continuity could arise from the cumulative arithmetic of weight control.