I do/have used a Kruve an I’ve been very surprised with by my findings with it. In my experience, even very nice grinders I’ve tried still produce like 4% fines, and some midrange ones are maybe only 6%. By percent, that’s significant enough, but in the end it’s less than a gram difference, and therefore sorta hard to use as the comparison between 2 grinders. Sifting is also essentially worthless for that purpose if you didn’t take the same measurement when the grinder was new, since you have nothing to compare the present to.
I honestly think your best bet is going by taste. If you feel the quality of your cup has declined, that’s probably the best way to be sure. Everything else is just a proxy for trying to determine how the cup will taste.