I'm somewhat skeptical these ever took place. For one thing there are military regulations that define punishment for dereliction of duty and these generally involve a court-martial. And executing someone after a court-martial is actually very uncommon.

Indeed if we look at the number of soldiers executed it's around just 300 for the British Army, 600 for the French, a mere 18 for the Germans, and zero for the US Army - and these figures include those executed for desertion and cowardice (both of which were far more common. Note that the Germans apparently had 150,000 men who deserted!).

http://ahoy.tk-jk.net/macslog/ShotatDawnWW1ArmyExecutio.html

If these killings did happen in large numbers then they were extra-judicial in nature; albeit I would personally comment that given the nature of the war I would see it more likely that the soldiers would "frag" heartless commanders who imposed such self-defeating policies.

More likely the Youtube channel is projecting Hollywood or Warhammer 40k sensationalism into the subject.