I hate to say this but this is patently wrong. I had a GTX 1070 and went from an i7 2600k to an i7 7700k and about doubled my FPS. for watever reason the new CPU really does feed the newer video cards much better. So statements like this are generally wrong unfortunately. I was SHOCKED at the difference because really I thought just like this.
I went from a core i5 3330 to a core i7 4770 with a GTX1070Ti and really felt little to no benefit at all at 1440p. Didn't take any benchmarks though...