Well you do get white, from the centre of the grain and the brown bits are from the other parts of the grain. This allows many millers to add refined white four to the mix, so you can't tell easily. They do this because white flour milled in high speed steel rollers is cheap. It is a process called adulteration and is very common. It's not as bad as the victorian times though when millers would add chalk, alum, plaster of paris, mashed potatoes and even sawdust into the flour, but not horsemeat as far as I know.