The Macbook Pros, as you state to use, don't have any vent holes in their keyboard. That's why you are able to use it without much heat increase. The Macbooks in question have the vent holes and need them for optimal performance. Apple knows about this limitation and that's why the GMA950 downclocks to 250Mhz from its default of 400Mhz when in clamshell mode. Your overall knowledge with these Macbooks seems to indicate that you have never used one for very long or examined one's interior in great detail. The article you posted indicates air exit vents, not air intake vents. It fails to mention the Mac Pro's intake vent at the front of the machine or the Mac Mini's and iMac's intake at the bottom.
Why are you bothering to argue about a model that isn't even in discussion on this thread? Whats the point?