as hexit said, if they have every game get same performance only based on CPU while completely disregarding game's engine and design then they are lying to you. If you wish to believe one source only, be my guest, however, I would think most people prefer to think for themselves.
some games are not optimised to use multi core cpu's, for example skyrim gets no benefit of running on a quad vs dual core. On the other hand game like SC2 gets a big difference depending on how many cores you got and what architecture they use. Skyrim is very CPU bound while SC2 is both CPU and GPU bound.
Doing benchmarks with varying CPUs while keeping everything constant is useful, but be critical of the results they give you. Ask yourself do they make sense.