I suspect it tests your monitor and monitor calibration as much as your color perception. In particular, sRGB displays have a pretty severely limited green gamut. If you have a wide-gamut display, the test is probably gonna appear different.
But another problem is with displaying the colors essentially full-window, which is going to be nearly-full-screen for many users. When we're staring at a screen with a particular tint, our eyes quickly do "auto white balance" that skews the results. It's the mechanism behind a bunch of optical illusions.
To address that last problem, I think the color display area should be much smaller, or you should be shown all hues at once and asked to position a cut-off point.
But another problem is with displaying the colors essentially full-window, which is going to be nearly-full-screen for many users. When we're staring at a screen with a particular tint, our eyes quickly do "auto white balance" that skews the results. It's the mechanism behind a bunch of optical illusions.
To address that last problem, I think the color display area should be much smaller, or you should be shown all hues at once and asked to position a cut-off point.