Body shape is not only about obesity, or fat, and I think it's obvious the author don't talk about this when speaking of body shape.
Maybe, but for sure the range of total size would be very different if everyone in the study was in shape.
It'd be interesting to see this study repeated after a decade of GLP-1 drugs being available (and cheaper).
Not sure. That level of size variance where the median falls off the middle seems to indicate a large extent of obese people.
The distribution in Japan would be very different.