There is no “prototypical” body type for a sprinter. This is clear when you look at Greene and Montgomery. All you need to be is strong. Some people just can’t put size on. It’s nothing against them, it’s just genetic. Explosive strength is the major component.
Also, with reference to the “sprinters are born” mentality. Yes, certain people are pre-disposed to being faster than others, that’s evident. But no one in the world will become Olympic champ on talent alone. You always need good, comprehensive, and above all SMART training to get to that level.