For a well known example of how this matters, consider the Pentium 4. Intel designed it with a deep pipeline on the assumption that they'd be able to reach higher clock speeds than was actually possible. At the intended 10GHz, the Pentium 4 would have had impressive performance for the time. But they couldn't achieve that clock speed, so they had to revert to the simpler pipeline design first used in the Pentium Pro and continue development from there.
> delays across different parts of the circuit
guess that's not "digital". After all i expect say gimp to run on my old linux 2.3 thinkpad or on a magnitudes faster i7, but of course with respect to the feasability of heavy effects and huge memory loads.
You purport to correct him and then you drop this phrase, which is questionable at best and wrong at worse.
You do design something that has different clock speeds differently. (Pipelining, power consumption, delays across different parts of the circuit). This is not anything too fancy, this is digital design/IC design 101.
Your post makes a lot less sense than his