As far as I remember from my army cadet days with SMLE's the charger was flicked out by the thumb imediately after pressing the rounds in using the thumb and the charger would not eject on closing the bolt, you could not close the bolt with a charger in the charger guide.
If wrong my excuse is this was 50 years ago.
The man in the video does well, but his buttstock is too short, placing his face too close to the bolt when retracted. I assume this is the reason he has to lift his head slightly every time he works the bolt. By doing so, he loses his 'sight picture' and has to regain it before every shot if he wants to aim carefully. Also he removes the second charger guide by hand; this is not necessary as it will eject when the bolt is closed.
Not hard to see how 600 men firing 30 rounds a minute could put 18,000 rounds onto a target in a minute.
That is the equivalent of about 30 Vickers guns! (IIRC their rate of fire is about 600 'rpm')
No wonder they cut down the grey illegitimates like a scythe in 1914.