I took the time to watch some videos of people testing this.

• A pneumatic roofing nailer couldn't stick a nail into the board from even 2-3cm away.
• A pneumatic framing nailer couldn't stick a nail into a pine board from 5m; the nails all tumbled badly past about 15cm.
• This guy then proceeded to weld a freakin' barrel, almost a meter long, onto his framing nailer in hopes of improving accuracy. While it did achieve that goal, he only got about 1cm of penetration from ~3m.
• A PA nailer with green blanks stuck a 1.5" nail into a railroad tie about an inch deep from 2m, and a 2.5" nail about 1cm deep from 3m.
• More interestingly, the above nailer only got about 5cm of penetration in a ballistic gel block with a 1.5" nail and a green blank from 15cm away. A yellow blank from the same distance got about 12cm of penetration.

Aside from all that, we're talking about a tool designed to push a fastener into material while in contact with said material. A gun is a tool designed to push a bullet into a target at a distance with some level of designed-in accuracy. These are not the same thing. A power nailer can certainly be used as a gun, but it can also be used as a step stool, a ruler, or a door stop. Usage outside intended purpose doesn't change the nature of an object.

Hey, if you want to call your PA nailer a nail gun, that's fine. There's no law requiring accuracy in speech, and of the entire power hammer category a PA nailer is probably closest.