This is an interesting discussion! I don't have a definitive answer for several reasons. Thankfully, I've never been in a gunfight. Also, I can only speak from my own perspective. As well, lots of skills develop with USPSA type practice, not any single one. What I've noticed as I've advanced is that my vision/perception has changed so I'm seeing more and faster. That appears to help in defensive classwork and sim scenarios. Things just seem to be slower. E.g. there's more "time" to decide if it's a gun or a cell phone.
As for the shooting, it's become easier to see the sight arc and know they've settled enough for another shot.
Is that all from shooting sub 2s Bills? Hardly.
Let's keep discussing!