Aim assist does not work?

[Péricles Maximus]

I'm playing this game again after a long time and since I'm playing with a controller I switched aim assist on. I was expecting something like Rockstar game like GT5 or RDR, where aim snaps to an enemy when you aim, but nothing happens. What could be wrong and how to fix it?

[Protectron]

Aim snap is in the game but behind a skill unlock (Gunslinger).

The Aim Assist is described by Undead Labs as "Adjustable aim assist, allowing the character to automatically lock on to the nearest enemy, can be set to ‘None’, ‘Normal’, or ‘Maximum’"

I have had it at Normal since 2018, but I play with k&m - so it isn't really needed.

Sometimes in close quarters battle with a Feral or lots of zombies, I manage to do very quick rotation movements and get killshots with one click of the mouse button. I feel that sometimes the cursor is not actually aiming at their heads when I fire, but the game still gives me headshots.

So in other words, I believe that Aim Assist on PC ensures that the hitbox of the nearest enemy is larger than the head appears graphically.