Mosquito test site is fake?

OK, so there's a thing going around, testing your ability to hear high-pitched noises.
Test at: http://www.ultrasonic-ringtones.com/
(I'm a little dubious about them using MP3s for this, since many MP3 encoders run high-pass filters over the source.
Secondly, at a 44.1 kHz sampling rate, the 22.4 kHz "mosquito" sound is above the Nyquist point.)

These points aside - I can apparently hear the 21.2 kHz sample just fine. Which I shouldn't be able to - my hearing is NOT that good, and even humans who *haven't* ruined their hearing over the years, shouldn't be able to hear that high!

However, the highest, 22 kHz, sample comes across as totally silent. This seems odd - I wouldn't expect the ear to have such a sharp roll-off from an easily-audible 21 kHz.

Looking closer at the 22 kHz, it shows up as silent on an oscilloscope! (I tried downloading it twice, just in case I'd damaged the first file)

So, yeah.. I reckon that test is a bit pants, and probably rigged. Or my MP3 player is wierd.