When we talk about paint defect removal we can talk about the leveling of paint, in the terms of removing large, visible variations in paint depth (orange peel, shrinkage, texture, runs) and also making the paint smooth like a mirror.
It is very possible uneven, non-level paint that still has a great shine, as well as having perfectly level, even paint that has little shine.
Wet sanding, for the most part, is done to make the paint more level. Large high spots are removed.
Jewelling on the other had will not removal orange peel and large changes in the variations in the paint, but will make the paint smoother by removing very small variations in the paint.
It comes down to how we define certain words. To some flat may me ultra refined like a mirror, and to others flat may mean like a prairie opposed to a mountain range.
Sanding will leave thousands and thousands of visible scratches, so in that sense the paint is not flat (again depending on the definition.) However if the sanding removed a ton of orange peel (even though there is still lots of little scratches) it could be viewed as flatter (then the orange peeled paint).
As far as the paint removed during jewelling there are a lot of variables that simply change the amount. I would say on most healthy and not crazily soft paints the amount removed would be significantly less the .1 mils, perhaps something like .02-.05 mils.