There's nothing incompatible with a car that can deliver 700 bhp maximum, and also 25 mpg, just not at the same time. I mean, Concorde was doing something not much off that, while in high speed cruise in the jet stream, and I bet that has more than 700 BHP.
Not that this car is an example of that, it's more or less unmodified and the advert is a patchwork of lies or self-delusion. Still, I think we all realise that.