People definitely have varying amounts of fat outside of their ribs or abdominal wall where you could probably call them big bones or small boned based on the composition. Although I think if you were to do a bunch of full body CTs of people, I think you would probably find that most people that are “big boned” are probably closer to normal portions than the people that are “small boned”

But as someone who has seen a lot of full body CT scans, the small skeleton in very large layers of tissue outside of the rib cage definitely exists, but that’s probably the notably rare exception.