I though I was clear about this, but I'll reiterate.

1. That the heuristic is accurate.
2. That the heuristic is more accurate than other easily applied heuristics.
3. That when the heuristic makes categories, the categories are backed by studies. These studies would show a statistical increase for specific health outcomes above this cutoff. That line would be tested relative to other proximal lines.
4. These heuristics would include different recommendations for different populations such as race, biological sex, and age.

A better alternative, as I had previously linked to, would be abdominal fat as measured at the waist. Easy heuristic and closely correlated to CVD.

All of what you say is true, but you're not address my particular issues.