You cannot create software without experience failure a hundred times a day.
Compare this to humanities like literature: how many times a day is a literature teacher proven to have made a mistake? How much real experience does this person have with failure? How many times have your literature teacher admitted "I made a mistake"?
So the STEM person is likely to be confident because s/he has a lot of experience with failure and know how to handle them, and how much they can delay progress.
Yeah, i think the author has mixed STEM as a field with tech-startups business side where hustling attitude is advised and often necessary to be honest.
If I had any literary skill, I’d write a tragedy in which the hero’s flaw is his lack of hubris. (Perhaps it would be autobiographical - my grad school advisor said my weakness is that I’m not arrogant enough.)