They say the same type of stuff about creating 'true Neapolitan pizza at home'. People with skillets and all sorts of crazy mess. But I learned a long time ago there is no real substitute for temperature.
I'm not a confused celebrity English chef making specious claims about skillet techniques producing 'Neapolitan' pizza. When 'they' say things, I'm not 'they.'

I've been eating NY style pizza, in all 6 boroughs, for 40 years, I've been studying oven thermodynamics for 15, I've been making my own pizzas in a home oven for 20 years (with a major discovery occurring 5 years ago, resulting in 4 minute pies ever since @550) and I've been consulting with aspiring NY style pizzerias for 3 years. When I say you can make authentic NY style pizza at 530 degrees, I'm not pulling it out of my butt. Unlike the skillet idiots who wouldn't know Neapolitan pizza if it bit them in the butt, I know exactly what authentic NY style pizza is and can produce countless examples of flawless 530-550 deg. 3-4 minute NY style pies.
A knowledge of materials science
can be a substitute for temperature. To a point. As of today, there's no known material that's consistently producing authentic fast baked NY style pizza at 500, but, give me a year, and there will be.
If you want to say that American style is more suitable for 500 degree ovens, I'm with you completely (for those uninterested in modding, of course). On the other hand, if you wish to stand behind your 650 deg. NY style claim by comparing my statements to the skillet idiots and talking about there being 'no substitutes for temperature,' then I disagree vehemently.
I have no knowledge of Varasano switching from KA. Nor do I know his motives. Or how he feels about it.
I'm sure you've read his recipe page, so you know at one point, he was a KA fan boy. Right now, I can show you videos of him/his employees using Harvest King. I don't need to know his motives or his inner feelings. Actions speak louder than words. For Jeff, Harvest King (Better for Bread) is a superior flour.
There is no serious question about whether KA is better than GM.
You're absolutely right, there is no serious question- GM is comparable or better. KA has better marketing and far better brand loyalty. But you don't make pizza with brand loyalty or marketing.
What type of vital wheat gluten have you been using?
As far as I know, there's only one type of vital wheat gluten. Are you asking me what brand? Over the years, until I came to understand the negative impact it was having on my bread, I used most of the popular brands: Bob's Red Mill, Now, Hodgson Mill and Honeyville.