To be honest, BSM does not give that higher of an advantage to players using it compared to players using the default Minecraft sprint key. However, seeing as it does actually toggle your sprint, you could count that as being a very big advantage for players who mess up their sprinting.
However, to counter-attack that, you could just say that Optifine has a big advantage over players who lag in FPS and the same goes for gamma for players who have low brightness and can't see in caves.
From what I can judge, I personally believe that BSM does not give that big of an advantage and the topic itself should certainly be revisited in terms of how much of an advantage it actually gives.
Nevertheless, it is not my place to determine whether this Mod does give an advantage or not - it is in fact the Administrative team that would deal with that.