While it is difficult to be certain, the lads do look quite clean and well turned out for a front line. Further, the trench does look to be "fresh", no water at the bottom, narrow, and looking at the sod cuts, and background, artillery hasn't gotten within several hundred yards of that line yet. Looks like an otherwise beautiful pasture that had a scar cut through it.

I don't dispute the excellent stereo, I do think the photographer may have been embellishing the caption a little.