That text reminds me exactly why I don't enjoy reading most car stuff written by Yanks. It's a needlessly aggressive tone he picks right from the start, and it's off putting to read as it automatically gets people's backs up.
Not sure what his point it, tbh. Slow cars are easier to learn in? Well duh. Slow cars are easier to handle at the limit? Obviously. Fast cars are really good fun to drive fast? Most of the time...
Personally I had more fun at Bedford in my MX5 with a whopping 130bhp than I did in a Cayman R on the same day. I'd built my speed up over the years too by starting out in slower cars before progressing, but the biggest amount of progression I ever made was when I owned the VXR220. Not because of the speed of the thing, either incredibly rapid compared to an MX5 or incredibly slow compared to a 458, but because it gave tremendous amounts of feedback. That's the biggest key to driving cars fast, is having a car that tells you what it's doing and then (and more importantly) being able to interpret that information into inputs.
I don't disagree that it's better to learn in slow cars first, but only because stuff happens slower. If the choice was between a Clio 172 or a TTRS, you'd be better off in the Clio. If the choice was between the same Clio and a Caterham 420R, the Caterham would teach you far more IMHO.
Just my thoughts any way. No right or wrong here, folks