I think I can clear the majority of this up for y'all.
Processors generate heat under load. All that heat doesn't get swallowed by some magical almost invisible absorption barrier in notebooks, it has to GO somewhere. In typical modern notebooks the processor is mated to a thermal transfer device [small copper or aluminum block mated to heat pipes] which carries the heat away from the notebook to the fans, which then expel the heat from the exhaust port.
In a fanless design, the heat sync is passive, which means it requires a lot of surface area to dissipate the heat. What has the most surface area on the macbook? You guessed it, the aluminum chassis itself. Per the iFixit teardown we can see that it's thermal pasted to a small heat transfer box that contacts directly to the chassis.
As such, it doesn't surprise me at all that the chassis would get warm, even hot under extreme loads. This means the heat is away from the processor, which is the desired result of CPU cooling. Hence, I'd actually say the "doesn't know ****" Apple employee probably DID know what he was talking about. (Hey, it DOES happen now and again)
Another thing to keep in mind is that, much like the SP3, I'm FAIRLY sure that the processor will be set to throttle early. In the SP3, the tJunction was something like 100-105c, yet it artificially throttled at 85c or so back down to 72. I say fairly sure because, until mine gets here tomorrow, there's no way for me to test it.
