Where is that documented?  It's certainly not in the manual of style itself, which clearly states that it's not prescriptive and defers to the article's editors.  (Quoted a bit above.)  I also don't see anything that introduces this precedent for the editors of subsections of the Manual to become a standing arbitration committee for every individual article (a supposition that clearly would not scale to the scope of Wikipedia); in fact, I suspect that's why we've gone to the trouble of setting up an actual arbitration process.