That's fair, but the air doesn't care what you weigh. It cares how much of that weight presents itself as frontal area. The topic on Slowtwitch is for a triathlon/TT fit. On a pan flat route.
You're 1000000% correct when we put it to road bike and toss some hills or terrain into the equation. Yes, at that point not looking at the w/kg part of the equation would be really wrong.
The reason the numbers were eye popping is that the math on what the CdA would have to be are about 0.33 according to Aeroweenie putting in the known power, weight, and tire setup. 0.33 on a TT bike is a parachute.
The photos of the bike fit, ain't no way that CdA is that bad. The fit was pretty good looking for a starting point.
I'm just incredulous at the whole scenario. The training stimulus to do 350w for a whole hour, no matter the weight of the person. And the speed outdoors on 330w on a decent looking TT fit. It's not a "you're lying" kind of thing. More of a "how is this possible". Genuine incredulity. As I've never met someone in real life that fits that mold, and I've met plenty of folks in 5 short years of riding.