Is that nonsense? Isn't it just saying that normal distributions are misleading when multimodal distributions would be more accurate? The indignant tone is unnecessary but it's not wrong to say complex systems cannot be modeled with a simple normal distribution.

Perhaps something like that was the intention, but it's not what the written text says.

Normal Distribution is a mathematical concept used in probability theory and statistics. It has nothing to do with any concept of "default humans".

https://en.wikipedia.org/wiki/Normal_distribution

It is simply saying the assumption of a normal distribution is incorrect for the population, which without context of what particular data they were observing would be impossible to know if it is in fact nonsense.