If the test is judging mindset, something that changes very regularly, of course the results will change as well. This is akin to saying testing blood sugar is worthless because the result varies throughout the day.
But people take the test once, and then use the results for a long period of time. Guess what? At night, blood sugar level goes down. it's no longer X. And likewise with this test.
Same thing, here. I wouldn't put much stock into a single result on a single test, but I think there's some broader value to be gained by examining the trend, the fluctuations, and what you wind up as more often than not.
The only assertion I have to disprove here is that the test is "worthless".