The goal of blending the butter into the dry ingredients is to coat some of the flour with fat so that it can’t react with the wet ingredients and form gluten. No gluten means a light crumbly texture. If you cut too much of the butter into the flour, you’re going to get a biscuit that’s so crumbly it falls apart when you try to eat it. If you don’t cut the butter enough, you’ll be stuck with a tough biscuit. The trick is to get it just right, or to stop cutting when the butter is the size of small peas.