I suspect that's the game's un-acknowledged version of the "contracting reticle" on other shooter games. You know the kind where your shot will fall somewhere in the aiming circle, which contracts in size as you hold it steady on one point.
It's a fair way to simulate realism...unless you already happen to know what you're doing. (Gritted Teeth!)
The only games close to FPS I play are the Fallouts. I am totally in the dark on the mechanics. But it makes perfect sense.
The one that drives me barXhit crazy is standing toe to teeth with a mole rat, having the barrel literally in his teeth, pulling the trigger...and missing.
A 50 cal into a poodle sized animal sucking a barrel should result in unidentifiable pink mist.