Very curious to know why this is in particular about barley. Reason for question is that I'm having a chemistry geek moment about it. Curiosity and the cat remember? Satisfaction brought him back?
I grind my own flour in Blendtec blender. Same amount of time every time so pretty consistent how fine it is, never sifted, leave all the bits and whatever in it. Have used 100% kamut, rye, spelt, einkorn, and barley. Barley shows dramatically more growth than the others! Most obvious is when I make waffles and stir up the batch a few times during its incubation. I usually go about 24 hours because I like the flavor so I get to see a long time course. The barley expands much more and more bounces back faster after mixing. Only difference I can think of is that only the barley is from local farm, less than 5 miles away, and very fresh i.e. harvested this past fall. The rest are from a commercial supplier though all grown in state I think.