[Locke64]

I think this is a case in which one has to read the intention behind the rules. The important thing this rule is stressing is that no mechanisms should extend above the bumper zone.
Though the following aren't as definitive as the manual, I think they do show the intent:
-The 'kicker' demonstration at kickoff was very tall, well above the bumper area, though it only extended beyond the frame perimiter below the area.
-One of the robots in the animation had a very similar design to this demonstration.