An engine will spin up to say 2000rpm without much extra fuel since it only has to overcome the friction of the engine. Different story when actually under load at the same rpm. When actually accelerating the vehicle the system will fail to keep up at a much lower rpm, perhaps even from idle.
The Ford solution gives me the impression that the air con won't make much difference in real time. That's why they needed a cold resoviour to accumulate the cold. Sounds like a bit of a cumbersome way to make more power. Average power is reduced since it's wasted on the air con. Loose power for a few minutes charging it up then recover less than the power you put in for a short period. Good for drag racing.