Maybe it's not fully precise, but I see the results correlative to my habits. Water weight was up a couple weeks ago. So I was more intentional about the water consumption, peed all the time, middle of the night (which I don't ever do). Next weight in, the water weight was down.
I also see the results in other ways like the fit of clothes, vs just a number on a scale, so I know it's working, and I am losing fat, despite losing lots of lbs each week.
It's part of the program, gives me something to work toward and be rewarded by, so overall I believe it's helpful in my journey.