People can claim what they want to claim, but if you check the actual output of the youtube video, you'll find the AAC audio track starts rolling down at 12 and is pretty much gone by 17. That's just how AAC works at lower bit rates. Bump it up to 320 and you might get up to 19 or 20kHz.
This video sweeps faster above 10kHz and stops very soon after that. I can hear a little ways beyond 10, but it's hard to stop it in time when it goes that fast.