I can think of two good reasons why reports of summary executions cannot be found. From the soldiers view they wouldn't want the next-of-kin to be presented with the "fact" that their son/brother/father/husband was a "coward". From the Army's viewpoint they wouldn't want it to be acknowledged officially that they responded in that manner. They certainly wouldn't write it in their official reports thus YOU can't find an example of such.

However many years later the last surviving soldier of WW1 decides that perhaps we SHOULD know what actually happened all those years ago.

I know I am not going to change your mind, or that of the professor. You are both too involved in maintaining support for your "masters"

I am more inclined to believe it did occur.