In every manufacturing process there are always chips that perform better than others. They all reach the "bin" that they're designed for, but the actual design is for higher than that, so that even imperfect chips can perform at the required level.
The corollary of that is that there are some chips that perform better than the design parameters would have you expect, they're easier to overclock and get higher speeds from. These are the "golden" chips.
Having said that, it's not clear to me that the M1* will do that, I don't know if Apple self-tune the chips on boot to extract the best performance, or they just slap in a standard clock-rate and anything that can meet it, does. I'd expect the latter, tbh. It's a lot easier, and it means there's less variation between devices which has lots of knock-on benefits to QA and the company in general, even if it means users can't overclock.
