He's right in way, but the camera at the time they started cooling it was already hot, so he's also very wrong as well.
the concept of this is to reduce the temperature delta over time in a sealed space by making the magnesium alloy colder.
We had a lot of people set them selves up for eating crow back when many were doubting the specs of the R5. I guess some still haven't got enough, so they are getting in line for a second serving
I like your article, nice and nuanced.
I have previously linked a thread to an astro forum. There somebody attached a peltier to his T3i without any modification to the camera itself, just pushed against the are behind the screen. They claim visible differences in noise, so a decent improvement in cooling. If that can be done even with the actual plastic body of the T3i, I don't see how the paint on the magnesium shell will hinder this solution from working at all.
Probably the most interesting question is what actually generates the heat. If it is the sensor, and that has poor heat transfer to the body due to IBIS, it may actually be a problem. But in that case I don't see how they pull off 20 minutes before reaching problematic temperatures, as they should have very, very little thermal mass.