I dunno, KL, I think it has more to do with the inherent philosophy of BSL than legends/histories of GM Ku. I think it has more to do with the kind of personalities BSL attracts. It's a complex system, especially when you compare it to something like Wing Chun. It takes a certain type of person to get to the end. The composition of the BSL 10 is magnificient, but I don't think you really get a sense of its brilliance until you complete them all and chew on them for a while. Also there's something to be said for the body type - most BSL practitioners are long and wiry, like GM Ku. I think the movements lend themselves best to this body type, just like Hung Ga lends itself to stockier stock. So maybe there's an ectomorphic quality to it, if you acribe to Sheldon (which I don't). Anyway, it's just an observation...