The rather puny "arms" supporting the "feelers" don't inspire confidence in me.
I wonder how true of an arc they swing for different size wheels.
It appears you need a "calibration wheel" to set things.
One problem with single "feeler" stands is they don't detect what's happening on the other brake track.
Depending on HOW you slammed into the curb with your underinflated tire, you still only see one side. You tend to crank on some spokes to compensate and find the opposite side is now even worse.
A 2 feeler stand allows you to see both sides at once and determine (somewhat) if they are bent equally.