Head shake is totally wrong, don't know what HT is trying to 'simulate'.
Having fired an LMG (Light Machine Gun, although it's anything but light lol) while in the Army, it was more the aim point would move due to recoil, but no head shaking. That being the reason we were told to 'double tap' rounds.
For an SMG on the few occasions we were allowed to fire it fully auto, a long burst would make it rise to the left, but yet again NO head shaking.
What should maybe happen is the longer the burst the more the sight 'wanders' off, to simulate the recoil from a sustained burst affecting the aim point.
But 'head shaking'?
Seems like he is trying to simulate the aim point moving but doing it the wrong way round, head shouldn't move, sight should.