The BOSS does not increase the barrel length. What it does is tune the harmionics of the barrel to a given load, rather than the shooter tuning the load to the rifle. While solid in it's theory, I believe that the shooting public has rejected the whole idea. I think that the shooting public wants to handload, and it they can't handload and duplicate the advertised results they will reject the innovation.
As for Warren't time, I agree, a lot of what he wrote about is obsolete, but lots of his theory is still valid. You can say what you will, but if you have two barrels weighing the same, same construction, of similar quality and differing only in barrel length, the shorter barrel will be stiffer, and thus it will be more accurate. That's just the way it is.