Attack Spill Radius Bonus Upgrade

Does anyone know if the "Attack Spill Radius Bonus" upgrade in Upgrade Editor works. And if it does, how is it applied tot he units? Does it increase all splash radii by the amount you set, or just the outer (25% damage) radius or just the inner (100% dmg) radius? And is it supposed to work at all or is it just leftover from an upgrade Blizzard originally planned but decided not to pursue (like "Apply Attack Upgrade Bonus")? Because I've tried using it, but had no noticable success with it, but perhaps I did something wrong, knowing how it works would help me avoid screwing it up. Thanks.

Damage spill distance is something else than the splash radii. I'm not sure what it's used for, though, perhaps has something to do with the artillery(line) attacks...

I know that the spill distance works, it's used for Vorpal Blades, but that's just in 1 direction. I need to increase spill radius to allow splash increase in all directions.

Spill Distance and Spill Radius are both for missile(line) and artillery(line) attacks. They determine the length and width of the oval behind the target unit where the attack does damage.