The competition has nothing to do with beyer speed figures.
Actually is does betplom because it is easier to run faster times when you are not under pressure (i.e., facing weak competition). Now I know there are other factors included in Beyer nuimbers, but generally speaking, the faster the time, the higher the Beyer, and to date there is no way of knowing if Big Brown could run the times he has vs. stiffer competition.