Did you make that up yourself, or did someone else actually get you to fall for that? Testing bread flour has nothing to do with the creation of the cookie.
The story might be apocryphal, but bakers indeed do use cookies to test proportions of ingredients. You’re not going to waste a whole pound of flour just to see the effect of more or less butter in a particular recipe. You do a little bit and bake them in cookie proportions. Specially when you have to make several hundred pounds of cake at a time, you can’t afford to err on the measurements, and you do need to know variations in the flour.
Did you make that up yourself, or did someone else actually get you to fall for that? Testing bread flour has nothing to do with the creation of the cookie.
The story might be apocryphal, but bakers indeed do use cookies to test proportions of ingredients. You’re not going to waste a whole pound of flour just to see the effect of more or less butter in a particular recipe. You do a little bit and bake them in cookie proportions. Specially when you have to make several hundred pounds of cake at a time, you can’t afford to err on the measurements, and you do need to know variations in the flour.