Open a couple of old drafting lettering guides (e.g. ones linked in sibling comments or TFA), and look closely. They'll obviously have a similar overall vibe, but there'll be tons of variations - differently shaped 3/4/7, where the curves start and stop on letters like CJGS569, whether the various corners are pointed or rounded or flattened, etc.
If your premise above is true, then we'd expect to see similar sorts of variations in the various fonts derived from drafting style, and TFA's entire point is that the author has collected hundreds of cases where we don't. Check his photos - they show the same font with the same idiosyncrasies, the off-balance G, two flattened points on the 4, the slightly asymmetric 8, etc. TFA is about the ubiquity of that specific set of letter shapes (modulo some variations that he discusses), not just of lettering that's generally in the drafting style.
(Also: in the best of faith and not meant as shade, you might want to look up "ad-hominem".)