Very definitely yes, I've seen changes. When I first did it a few years ago, mine was by far the worst, my two sugar-craving-est kids were next, then the next two, then my superh ealthy, naturally-low-carb-his-whole-life dh. He had nary a string or bubble even after ten minutes, while I had long, disgusting strings instantly (no waiting).
After a few months of being sugar-free, mine was dramatically improved. I haven't taken it in a long time to see an update.
I don't know if it actually measures candida or not, but there was most definitely a correlation in our family between sugar obsession and spit test results, and I most definitely saw a change. It wasn't just a coincidence on those particular days, either; I replicated the test several times and got stringy every time, then repeated it several times several months later and consistently got no strings.
OTOH, I never had thrush or a white tongue, and got yeast infections only after the last few rounds of antibiotics (after many over several years) when I forgot to take tons of yogurt each day during the round. Never got them again after that. So I don't totally know how much candida I had, systemic or otherwise.
5'4" 39yo mother to five sweeties & married to their AMAZING DaddyGrok
Deadlift: 225lb x 4
Bench: 125 x 2
Back Squat: 155 x 2
Overhead Press: 80 x 1
Determined to beat binge-eating disorder no matter what it takes!