The dominant discrepancies are "expected" fat (boobs, etc), and "unexpected" muscle (cyclists, body builders, hard labour careers, etc). I'm currently around 10-15lb overfat and 40-50lb overweight [0]. Only the former statistic matters.
[0] And that, at least somewhat, tracks visual perceptions. Nobody looks at me with a shirt on and believes I need to lose weight, because 10-15lb isn't _that_ much extra on a tall frame. If I were 40-50lb overfat then that would be painfully obvious regardless.
What is the line for "overfat" in this framework?
In my mind, it's equivalent to subtracting a coarse estimate of how much extra muscle by mass I have compared to the median adult male they're using to construct BMI charts.
My actual methodology is pretty crude though -- when I was 15lbs lighter I had borderline visible abs and other visual indicators of being around the 15-20% body fat mark, and aside from gaining weight I don't have any reason to believe I've had any notable muscular atrophy since then, so I'm estimating the actual excess fat in that ballpark. It's be easy for numbers to be off 10lb or more, but even then it'd still indicate the overfat surplus being much less than the overweight surplus.
A better methodology uses calipers and various skin measurements to estimate true body fat percentage.