Every 'corrected' dyno figure is what the car made, then adjusted to suit a certain set of atmospheric conditions. In reality a car making 150bhp at 25oC might make only 100bhp at 90oC (depends on the car) so the corrected figure adjust's the power back up to the what the calculation say's it would've made. And that's the big problem, it's based on what the calculation dictates.

The ECU will compensate but only to protect the engine, for example if you tried to dyno my car in 90oC heat it would be pulling ~5-6 degree's of ignition whereas a N/A engine may only be pulling 1-2 degrees or even none at all.