Good point. :) I guess it actually has to be something more like "comparative overconfidence", i.e., confidence in your own scientific ideas or assessment of your general ability to produce scientific output, relative to confidence in your other skills. Theoretical science (including e.g., decision theory, FAI theory) has longer and weaker feedback cycles than most business fields like running a pizza parlor, so if you start off overconfident in general, you can probably keep your overconfidence in your scientific ideas/skills longer than your business ideas/skills.