ok here we go, i would like to say that i am in now way affiliated with any hood company. i am a mechanical engineer and this is just my thinking using what i wave been taught and seen in some tests.
as far as the hood scoop not getting any air:
when a car moves through a compressible fluid (air) it build a boundary layer that deters the fresh fast moving air from directly contacting all parts of the car. this event is described in the first picture and demonstrated in the picture of the viper...
the large gap between the hood and the stream of smoke is i believe leading you to think that the scoop would not get any air... but if there was a hole in the hood with a positive suction (like a sealed intake pulling air in) the fluid dynamics gets a lot more complicated.
From this image you can see that there smoke entering the "slot" in the cowl but at this point every application can be different. i believe this is the reason dragsters put the intake so high off the surface of the car. but like i said with the positive suction and cooler air coming from somewhere other than the engine bay it should see a performance gain. and there have been many debates on this site and other about the possibility or "ram air" intakes, at the speed the cars are moving it really is not fast enough to get the pressure needed to give a ram effect. so the idea is just to allow the intake the most non-turbulent coolest air it can get...
Now for the vents:
judging from these to images
and the fact that the grill on the camaro is much more of a wall, it would tend to move the air very well through the engine bay. this redirectio on of the air path can/will have two effects. one the heat will be carried out of the engine bay as it was designed to do. but in addition it will changed the basic shape that the air must travel around.
by having the air able to pass through the grill and then leave from the hood the air will take a path less like the top illustration of a "flat plate" and more of an angled surface...
these are my thoughts on the subject...