Sounds pretty broad but thats only 3" W x 18" H at 100yds and as the trenches were at times only feet apart in WWI didn't matter even at a 100yds at a centre mass shot you've a good chance of hitting the target.
I am wondering if it was the same criteria for WWI production rifle and given the length of time between the World Wars whether they improved the requirement basically what I am asking were the WWI production rifles and more or less accurate than a WWII production rifle just curious.