The authors of the RB and BB were a couple of dedicated hobbyists who, with the help of other dedicated collectors like Steve Stephens, compiled the information contained in the books. What is presented therein is mainly the result of their collective (no pun intended) empirical observations, since much of the literature available in recent years had not yet been found then. In other words, what's in the books is just what they had seen. But in some cases they also extrapolated and listed some items (sizes) which don't actually exist. While I appreciate the noting of a comparative example of such, I think we need respect the OP and not shift the focus to militariana.