That a entirely different, and generally game agnostic, thing.
I don't know their comparison metrics, so I would only be guessing. If the claim was "The graphics card in the PS4 performs 50% faster" I could make sense of that, because I could use graphics as a comparison point. However, "The collection of hardware performs 50% faster than this collections of hardware" ... doing what? Across everything it averages out to 50%? It can run its respective OS 50% faster, or stream textures 50% faster, or load objects 50% faster? It can processes data 50% faster, or update the screen image 50% faster? It can do all of the above, 50% faster?
It just seems like such as strange statement. "The PS4 is 50% faster". Ok, I can understand it being generally better, what does the statistic mean?
Coupled with statements such as the Xbox 360 being 'faster' than the PS3, I have no idea how useful this information is. But that's just me, trying to wrap my head around why I should be excited.