I'm unaware of that view on brunettes but can say brown hairs vary from being really dark like black to a light brown.
The colour can be  light brown to almost black hair.
I wish my hair were nice and brown like my youngest daughter, but I have dirty blond instead. Well, you don't have the second most common hair color for people though! I actually wish I did, I think it looks better on me. What else can you tell me about brown hair?
It varies from light brown to almost black hair.