Sure but the difference between cards is often just a few FPS. Look at the 1060 vs 480/580. Same for Fury X vs 980 Ti in some cases.
Psssssh. Don't ruin the fun of people bragging it's OVER 15% FASTER!!!!!11111 even though that means only, I don't know, 5fps difference which is already beyond 60fps threshold to begin with...
Which is why I really don't like percentages, because they literally skew the perception of differences. 15% sounds like a lot, but if someone says the difference is 5fps, it's like whatever, margin of error almost if we are realistic.