The thinner (brown) fibers allow the arrow to drop into the fibers much easier than the older style.
How can that be when the brown fibers are only found on the top and sides?? The original black fibers still support the arrow from below. It is possible on either type of bisket for the arrow if bumped to slide up int the bristles but any time you draw the arrow, even slightly, or tap it with your finger, it silently slides right back to the center of the bisket ready to shoot.
This is an absolute non-issue for any and all bisket owners, and I'm guessing that Len doesn't shoot a bisket, new or old style. Either that or he is a litte paraniod.