I've seen some recipes that call for AP flour and bread flour. What's the point of that?
Assume AP flour has 10.5% protein and bread flour has 11.5% protein. If a recipe calls for equal amounts of AP flour and bread flour, you'll end up with a mixture that is 11% protein. Why not just find 11% protein flour in the first place?
Also, since the protein amount of flour vastly differs by brand, region, etc. -- how can a recipe make any assumptions about the final protein amount in the flour mixture.