I know i haven't misunderstood hit chances or something like that because of how i discovered it : i was using a coil gun to shoot at an unaware cave ambush(1 programmer 2 hunters) through walls so that they couldn't fire back. After killing the programmer, i noticed that the hit chance when shooting on the programmer's now empty tile was significantly higher than when shooting at the tile right below it, where there was a hunter.
How to use effectively :
First, don't shoot at a garrison barrier, instead position yourself somewhere else so that you're shooting at a wall when doing this. I use energy weapons to avoid wasting matter.
Then, once you know what's behind the barrier, you can prepare yourself adequately before fighting them. For example, by equipping a launcher to fight swarmers, or the correct relay coupler to assimilate hunters.
You could also use that in caves when you don't have a sensor array to detect whether an outpost/checkpoint is controlled by unaware or derelicts, or to know the composition of dormant bots in an outpost(though you wouldn't be able to differentiate between dormant bots and disrupted bots)
By the way, i shoot using the mouse, maybe that's relevant somehow. I also might've had a terrain scanner with me every time, but i am not sure.(also i play on Linux using proton)
Next time i get to a garrison, i'll take a screenshot if that's not enough info.