Any improvement like that is from the GPU being given different kinds of circuits entirely. The raw performance difference is not very impressive. In late 2012 you'd get about 8 gigaflops per dollar. Late 2017 gets you almost double that. They're being used somewhat more effectively, but a normal non-neural-net benchmark shows a total performance improvement of... 3x.
They're doing better than CPUs but they're still falling behind Moore's law.