They aren't myths. If you take the same chip and clock it higher it's faster. Otherwise nobody would overclock. Second, more cores is better in multi threaded benchmarks, again, looking at the same architecture and generation of chip, just adding more cores. Sure, between 2 different designs, you can't compare core count and clock speed, but maybe M3 is very similar to M2, I don't know. But myth, that's really not correct, either.