"Do you and Raggy think he is lying in clearly stating the above fact?"
No I don'r but I believe that he could easily have talked to and fought beside people who knew about the executions first hand - do you consider this beyond the realms of possibility and that he was either lying or a gullible half-wit?
At no time did Patch claim to have witnessed shellshock why are you harping on him "witnessing it" - he makes it clear he didn't.

why are you suggesting he said something else - do you dislike and distrust veterans so much that you feel th need to twist their words

Once agabi, this is what he said -
"You were in that trench. That was your front line. You had to keep an eye on the German front line. You daren't leave. No. I suppose if you left, and some of them did, they were shot as cowards. That is another thing with shell shock – I never saw anyone with it, never experienced it – but it seemed you stood at the bottom of the ladder and you just could not move. Shellshock took all the nervous power out of you.
An officer would come down and very often shoot them as a coward. That man was no more a coward than you or I. He just could not move. That's shell shock. Towards the end of war they recognised it as an illness. The early part of the war – they didn't. If you were there you were shot. And that was it. And there's a good many men who were shot for cowardice and they are asking now … that verdict be taken away. They were not cowards."

Still not find any official denials of these executions? - must be all your own work then
Jim Carroll