To be perfectly honest, the "exact" amount might not mean a heck of a lot as far as cheese, onions, etc., etc. In fact, except for items like adding extra nuts, "exact" measurements are probably most necessary in baked goods. There's not much fooling around there.
But again, my point wasn't that a recipe would be ruined by the "handfull vs. 1/3 cup" of cheese, but more that it's not a good message for a TV cook to send unless it's prefaced by the point that the amount doesn't matter. To those of us who have been cooking for a long time & realize the difference it's fine, but it could provide disappointing results to someone new to the joy of cooking. Again - regardless of the size of your hands, unless you're a small child, 1/3 cup does not equal a handful of grated cheese - lol!!!!