I propose a mechanism that brings about the difference: Higher speed cracks the brittle beans differently, smashing them into a higher proportion of fines. Fi

I propose a mechanism that brings about the difference: Higher speed cracks the brittle beans differently, smashing them into a higher proportion of fines. Fine and coarse particles yield very different proportions of compounds into the water – the less soluble stuff kind of only washes off the surface of the ground particles. Finer particles, more surface, more of the hard-to-extract less soluble stuff.