He's not really referring to super fine particles as much as he's referring to the sort of lengths a cow would normally get when they take a bite of grass on pasture. The part that I find most interesting is that if the animal is continually being asked to digest longer forage than it is comfortably capable of digesting, it grows its digestive system to accommodate that forage. Problem is, that new gut growth requires more maintenance calories, so now that animal needs to digest more of that stemmy forage yet just to maintain. First explanation for those gutty runt calves that has ever made much sense to me.
I'm working on digging through the researcher referenced (he has ZERO papers on this) to find out what is out there in research land.
If you're interested I will get your attention and then I'll share what I find.