Okay then, ASSUMING that a fat person is less aerodynamic than a skinny person, then yes, obviously an aero bike will be a smaller percentage of overall drag for the fat person. This is more a question of how percentages work than it is about anything else!
It wasn’t a question.
Just adding some fuel to the fire here:
Frontal area isn’t the only consideration as to whether “fat” vs “skinny” is more or less aerodynamic. The fat guy could still be more aerodynamic.
Could be, but likely isn’t. Unless he’s a really weirdly shaped fat guy. Maybe all his fat is on the back of his head, in a teardrop shape. Then he could ride helmetless and be quite aero.