Detecting gravitational waves requires extreme precision. Pastries are in the ordinary precision range. :)

Joking aside I suspect if you are good enough where the limiting factor in your baking is the precision of butter specified as opposed to sloppy techniques you are better off using a recipe written by a professional pastry chef for other proficient bakers. In my experience they usually write quantities in terms of weight and recommend measuring it that way.

For example Claire Saffitz calls in her Confetti Cake recipe for "3 sticks unsalted butter (12 oz / 340g), at room temperature". That would indicate that the 100g approximation is 13% low.

I make a lot of pastry, actually. I've even gone to school for it, though I don't do it professionally now. Variable moisture content of flour is a bigger variable. I can't think of a case where someone would be using sticks of butter and 100 grams is not close enough.

If you're a commercial food manufacturer with a factory then yes. For everyone else up to "professional with a pastry shop" it's way less dire then you make it seem.

When you care about "extreme precision", you should also buy the same brand over and over again. In such case, the difference in sticks will not exist.