How much fat is “surplus”?

Have you ever met skinny people? Even when I was at my thinnest, my body did jiggle. Not because of fat or stretched skin (at my fattest, I have still been on the lower end of normal weight), but because relaxed muscle jiggles too, unless you have muscles like stone. Which you cannot really have, if you are underweight, which people in this thread seem to think is "skinny".

Also thin is not the same as healthy, nor beautiful. People with anorexia are really thin, do people think they are healthy? Or cancer patients. Or someone like me, whose "miracle diet" is autoimmune diseases combined with mental health problems. I am all bony to touch, you can see my ribs and a tight gap. My cheeks are sunken in. I still jiggle.

I wouldn't call it "surplus", mind you. Gimme the ones with a belly, all genders.