Pony, I have taken a whole lot of courses at Frontsight. It is a square ranged based fundamental marksmanship school. The skill sets taught there have very limited success inside of the crucible of FOF. This is what Armstrong is getting at.
You must take your fundamentals into FOF to understand how limited the skill sets are against a live, thinking, non-compliant, fighting adversary. I have trained with hundreds and hundreds of guys that have done this. To a man, they realize that the fundamentals have very little to do with the realities of a fight. They are absolutely necessary, but it is just a starting point.
You have asked for proof. I do not know how to give it except to suggest that you follow the link in my sig line. You have just been introduced to an open door at Frontsight.....there is a whole world inside of it that you have no idea of.
The fundamentals are just the beginning. Do not make the mistake to think that they are anything but. The training that I got at Frontsight got it's rear end whipped inside of FOF. That has happened to every person, with that type of training, in the FOF that I have witnessed or participated in. This includes Combat Masters and Frontsight instructors. You need to realize that many hard core Frontsight and Gunsite Modern Techniquers have had the FOF epithaney and now train well beyond the fundamentals that these schools teach.
There is a world of evidence in these facts....you are just not aware of it due to your newness to training. Follow the link it will open up an entire new world.
I have read plenty of Tom Perroni's stuff. He goes way past the square range fundamentals also.