Slovik's death was one part of maintaining that discipline. Everyone in the army had to know that if they walked away they would be shot, and shooting Slovik showed that the army was serious about it.
But once a retreat turns into a rout that is no longer the case; assuming the general manages to rally the army and re-establish discipline there is no point in shooting half the remaining troops. Maybe he shoots a few of ones who left early, just to make the point, but mostly he has to carry on with what he has got.
I only read a single account in a publication from sixties, allegedly from one of those judges who was the career barrister, and it was allegedly a confession written in his last will.
The death count will go into hundreds of thousands, a far from small part of the whole allied force.
Soviets, on other hands, possibly executed close to a million of own troops, including generals, but it did not stop the extreme desertion rates.
It was very dangerous to suggest not exterminating any person or group. Eagerness was evidence of commitment. Everybody needed to provide such concrete evidence of commitment, or be labeled a class enemy.
The official wartime data is 10000 troops in "penal forces," and 158000 by post-war Soviet count, which is already a giant number, and does not include penal troops whose execution were never recorded, or ones who died in human wave attacks or after being ordered to stand ground under fire from, some times friendly, artillery.
The entire losses of penal battalions may range from 100k to 300k by calculations of historians.
But executions and fatalities from de-facto penal actions were not only limited to penal forces. Any war veteran who served in an any much sizeable unit can tell of battalions loosing up to one in ten men to "disciplinary actions" akin ones practiced by penal forces.
There were few well written about cases (which I cannot remember much about though) when entire deemed "low morale" units were sent for certain death, being "spent," drawing artillery fire or ordered to march on enemy armour in the open without any anti tank weaponry.
A matter of fact trial and execution
My point however was the killing of a person by their own government during a time of war. This guy could have gone on to do all sorts of things to support the effort. He self reported his own desertion. Killing him was sick.
And you can contradict me all you like, but the whole article is about how the people that actually made the decision and had it carried out, regret it.
German production of aircraft increased every month right up to the end of the war, although they ran out of pilots to fly them. Armor and infantry won that war. Fighter planes blowing up locomotives had some effect, toward the end.