Why is full frame viewfinder info smaller?
I have no idea, but my guess could be that the crop sensor cameras' viewfinders are more magnified? So the info down the bottom appears larger?
Inversely the larger FF viewfinders don't need as much magnification, so the info on the bottom is longer and smaller?
You can always fiddle with the diopter adjustment if you're finding it hard to read (I'm short sighted but I find it easy enough to see)