The things I notice are:
a. the bloke facing towards the rear of the trench in the foreground is looking at the bloke standing above ground in the upper left corner of the first picture.
b. the photographer is obviously above ground in both pictures and has moved for the second photo.
c. there is visible smoke (shellburst?) in the distant background and what appears to be structures on the skyline of the first photo. All that is obscured by smoke, real or added, in the second photo.
d. the one visible shoulder flash is a vertically aligned 2 colour rectangle. 5th Div AIF had vertically aligned shoulder flashes.

My suspicion is that these are actually 5DIV troops in a rear training area performing a scripted manoeuvre.