The discussion is somewhat moot, what did bug me is that the article claims those are typical tolerances inherent in the machining / wire edm / molding processe

The discussion is somewhat moot, what did bug me is that the article claims those are typical tolerances inherent in the machining / wire edm / molding processes whereas it just may be the tolerance that is applied if nothing else is agreed upon. You can achieve much tighter tolerances if needed, even in mass-produced stuff like LEGO bricks, plastic lenses, iphone / macbook cases, PCBs, etc...