Yeah, it's wrong
Have a look at what
@gpseymour did, and if it's still not clear I'll do a quick how-to...
Anyway...
There's no way on earth you'd punch to that tolerance.
Might be just possible to precision broach.
Even standard consumer grade laser would struggle with half a thou to play with.
Best way for production for that tolerance would probably be grinding.
The reason why do it by hand is because it's part of the training - get stuck somewhere with a broken critical component and all you have is your toolbox - carve the bit by hand.
All it has to with a katana is a facetious way of showing that a file isn't necessarily just a general use tool.
Technically, there's one grade of bastard file - it goes coarse>bastard>2nd cut>smooth.
Grab a bastard and you know it'll be more aggressive than a 2nd cut, but a bit finer than a coarse.
It depends on which cut pattern though, and I do know that an awful lot of Americans just call any flat (and tapered) file a bastard. Which is wrong. Even if referring to a file from the American cut pattern set...
Bastardisation of the bastard if you ask me
Oh, and the patience is also part of the reasoning of the square plate apprentice project - and another reason why it's maybe not a good idea for a non-DIY person to go at.