Interesting read.
My take was that they found 24c tires needed to be pressurized higher to avoid pinch flats on the cobbles. 28c tires could be run at lower pressures and still avoid pinch flats but if too low lost speed. So a 28 could be run at lower pressure and thus would be more comfortable than a 24. I did not get that the lower pressure tires were faster on pavement though, considering they were trying to overcome the cobblestones at Roubaix. Perhaps I missed something?
I get that concept, having read and understood the J.H. theory of lower pressures absorbing bumps rather than deflecting to increase speed, but road tubulars and Compass tires are different beasts than Marathons and I honestly wonder at the amount of absorption they would create at moderately lower pressures, if we accept that too low would make them sluggish.