DDR4 has standard operating to 3200MT/s this mean models between 2666 and 3201MT/s are not "overclocked". Intel make artificial limitations to milk fanboys for more money for expensive parts.
Is limited by only 300 watt bioses and lower frequencies. I think that will be change soon. 3090 and 3080 has bioses for 400-450...also maybe for more watts? When see results with 6800/6900 equiped with modded bioses maybe will be got more fair comparison and will see also where is limitations...
Overclocking of CPU is death from few years. Increase of frequency with 10-15%(when is possible) ≠ 10-15% more performance in tasks. What is positive to got 3-4% at "OC" of CPU and 1-2% at OC RAM when for that you spent +30% more money? Yes more OC is possible for the purpose of competition...