It wasn't that he screwed up a minor thing off the top of his head, he had fundamental misunderstandings on how to approach the problem. I doubt that's the case for your 8+9 example.
What exactly is your point then? Do you not think "great" people occasionally have "fundamental misunderstandings"? Who determines what is simple? Who determines what's fundamental? I also find it strange that you give the physicist a pass in my example, but not the developer.
If someone makes a mistake adding any two 3 digit numbers in their head are they not great? After all, there are people in grade school who can do this easily.
There's a huge difference between messing up a small piece, and not knowing how to even approach a trivial problem in the field. Do you not see the difference? Like, this is way more like Francis Crick asking 'what's a cell?' than screwing up a math problem.
