I'd check if the curved part matches the curve of the air box, like I think Scott points to. Or check for a profile match. I think the purpose of the block outs is to direct air to the radiator, away from the side panels, past the engine, then out the vents. Sometimes there are block outs behind the air vent to prevent air passing it, especially if you have vents in the panel in front of your legs.
Maybe for wiring where they pass sharp metal edges.