My confusion is less on the thread size, and more about the thread direction, what are the benefits of having it be the french/Italian way?
Sounds more like a disagreement on the fundamentals of how to put a bicycle together, than a disagreement on standard tool/part sizing.

Also as vintage cellar alluded to, I think if they marked bikes with specific threading info rather than marking swiss/french the exact same and then interchanging it willy nilly (like motobecane did) there would be less frustration/jokes about french standards.
Not like im upset, the reason i want to build an old french frame is cuz i appreciate all this weirdness...but weirdness begets jokes sometimes