I'm not sure who invented it...but I'm sure it's been around for a looooong time.
If people look at you and think your nuts for using it...they really don't know much about the tradition or history of archery.
I'm not sure why you feel it reduces the effort to pull your bow back...but if that's the sensation you're getting...awesome!
Shooting 3 under does place the arrow closer to your eye...so you use it more effectively...consciously or subconsciously...depending on your aiming techinique.
It also reduces your point on so you can use it more effectively at closer distances.
It's a great way to shoot...but I personally prefer split finger because it gives me more control of my arrow...when trick shooting or stalking.
Ray