Sounds like a lot of work to save a dime. Of course the total amount of currency involved could be lesser or greater I guess... but ether way it can't be much.
Of course in my calculations I don't use specialty finished 11 speed chains or anything like that. My KMC chains purchased via Amazon aren't much more than about ten bucks. So if I repeatedly replace the chain about ten percent too early.... every decade it would amount to a whole new free $10 chain. Of course a less than perfect measurement/replacement procedure would more likely mean a five percent ether way error. Early replacements would cancel late replacements.... and little to nothing would change.
I don't know why cyclist fret so much about the disposable parts.
I sure hope you don't think I'm "fretting".
I'm simply asking - from someone who might know and explain - whether the tool gives a false positive or false negative. I'll leave it up to myself and others to decide whether to "fret" about the hassle of chain wear methods or chain replacement.
Myself? I don't sweat a few bucks here and there to save time and effort. But, I don't think it's so dumb that with about a dozen chains to keep track of, it's worthwhile to have a dead simple and quick screening tool as long as I know which way the potential inaccuracy goes.