They’re not talking about the results. They’re saying the gulf between the skill and strength required to go from 11s to 9s is larger than the gulf between 11s and 15s - that’s because it takes exponentially increasing effort for marginal gains as you approach world record times - it’s not a linear thing and thus looking at the output paints a really misleading picture on the relative difference in inputs
Verbatim quote: “The difference between me and an average Joe in strength technique and speed was still less than the difference between me and the Olympic level athletes that I occasionally competed (or worse, trained) with.”
I’m not disputing the gaps in technique, just to be clear.