That's certainly true for the systems as tested in this review but it probably doesn't give a representative view of a serious gamer's experience with a high-end graphics card.
Imagine how well (or poorly) the GTX750Ti in a typical Pentium 4 system would perform!
My HD3850 AGP card virtually doubled in performance when I switched it from a P4 3.06GHz machine to a Core2Duo 2.4Ghz (both with 2GB DDR400 RAM), but it was pretty much maxed out at that.
You really need to match components in order to optimise and benefit from their respective strengths.