Working on HPC field and with generations and generations of Intel hardware, I can tell you that two node difference (alone) never gives you 25% real world performance in the realm of Intel, let alone theoretical.
Real world performance pretty much always lines up with these estimates. It's the main reason why we have exponential growth in computing power in the first place.
It would be a more fair comparison to compare the M1 to AMD's ZEN 4, which should be coming out next quarter.
[1] https://www.tsmc.com/english/dedicatedFoundry/technology/log...
This is jumping from Intel's heroically old 14nm+++++++++++++++ to a brand spanking new TSMC process. It might be on the order of 4 to 6 times denser.
We've seen how the latter went until AMD came back to the game.