The main thrust of the 3 articles your provided links for is to convince people that if your engine is designed for regular gas, there is no benefit of using premium and you should stick to regular. That sounds OK. But at no point did any of the articles address the situation found in most Toyota V6 engines, which are specifically designed to run on regular OR premium, and according to the Toyota owners manual, the engine will deliver more horsepower with premium. The articles only focused on engines that were designed to run only on regular, concluding (rightly so) that it would be a waste to use premium in these vehicles.
In fact, one article actually says that one could use regular even if the engine is designed for premium, so that pretty much throws into doubt everything else in the article. Here is the exact quote:
"Even if you have a super-performance sportster with a big "91 ONLY" sticker on the gas cap, no harm will likely come if 87 is added by mistake."
Now this "may be" true for some engines spec'ed to use premium, but certainly not all engines, and it is very poor advice. If your engine is designed to use premium only, that is what should be used.
Regarding my original point about an engine running cooler on premium (or "not cooler" in your opinion), you seem to playing games with the facts. Look at this way--if a Toyota V6 engine delivers more horsepower with premium as Toyota claims (my dealer actually made me sign an acknowledgement of this fact when I took delivery of my V6 Camry), then for a given vehicle speed, less fuel will be used because the premium delivers more horsepower for the same amount of fuel. And since (as you said above) premium and regular have the same BTU content, then less heat will be generated with premium assuming that the vehicle is traveling the same speed as it would be with regular fuel.
This is what the magic of higher octane does. It makes the fuel burn slower to deliver more power and better mileage (assuming that the engine is designed to take advantage of the higher octane). Since premium gas burns slower than regular at the same vehicle speed, there is less heat generated as a byproduct of combustion using premium fuel.