Very early on in my baking follies, I remember being told to spoon and sweep. As I’ve evolved as a baker, I now rely on weights. Not all cups are created equal, so that alone can mean the difference of an ounce or two.Scooping vs. sweeping is a whole other ballpark. Using one set of my measuring cups, the difference is just under an ounce.
Ounces matter in baking. To be even more precise, grams matter in baking, and there are 28 of them in an ounce, so a recipe with a variance of 2 ounces either way, will certainly affect your end result.