alt Hacker NewsA significant portion of the Apple Silicon efficiency gains would have come from shifting away from discrete GPUs. At that time it was very normal for the integrated GPU to be minimal (slow) because people who need it get a discrete GPU. Things are very different now because we push far more onto the GPU now vs. back then, which made Intel and AMD scale them up out of uselessness. Now most people don't really need a discrete GPU because the integrated ones are fast enough to even handle some gaming.
The majority(?) of Intel MacBooks didn't have dGPUs though. That was a higher-end option on the larger models. I also vaguely remember there being a big leap in iGPU performance with Intel Iris around 2013. I had a high-end MBP from work and wished I could perma disable the dGPU, cause I didn't need it and it just made the thing get hot.
But yeah, the remaining people who needed dGPUs can now just use the integrated AS graphics, so they'll notice an even bigger difference.