>Getting all the way to the obese BMI range while having healthy body fat is only happening for people with an extreme dedication to body building and diet

And sumo wrestlers.

The line seems to be drawn at (effortful) activity level more than anything else. And BMI doesn't say anything about that.

I think the vexation comes from the focus on an attribute that is not directly mutable, per one's agency, because that's easier to sell things related to. Versus action that you have a lot more direct control over (social or physical circumstances notwithstanding).