I also tried the single point of contact on my first m4forgery, I found it sounded better on paper than it was useful in real world transition.
I only posted that to add information to the subject from one of the most respected trigger pullers out there.
As for the three point, essentially it's an additional tie between the to two contact points. Here
is an example.
I don't think the three point is mandatory, but I do, personally, prefer the two point sling combination.
To each his own, and if it works for you, kudos. I liked the single point sling, ordered both a special attachment and a special sling just to try it out. I went to the range one day, worked from low ready, to firing position to throwing it over my back to "attack in another direction" type of evac and found that I personally didn't like it.
I was out a couple of hundred bucks, which was something that I can afford as part of a D.I.N.K.s household - but it still was something I wasn't expecting.
I was merely trying to share some experience that I learned the hard way.
If you like the single point contact, I am happy for you and hope it is everything that you are looking for/need in a SHTF situation.
Personally, I like the standard two point with a quick release. It's perfect for everything I personally see myself doing and I can get out of it with one push of a button.