>attracts a certain type of person, and intimidates another. And it may be that it intimidates more women than men.
This is classic horseshoe theory, where extremists on both ends of a spectrum actually wrap around and start to sound the same. In this case they both believe that women are delicate flowers who can't handle the pressure, stress, and competition of the working world like men can.
There's a difference between "lower self-confidence" and "can't handle pressure, stress, and competition". It's also possible that even women who have high self confidence in their abilities are less confident that they will be judged positively by others.
There's plenty of research to the effect that men will apply to a job if they meet 40% of the listed requirements, whereas women won't until they meet 90%. And when you don't meet someone's default expectations of what kind of person a "software developer" (or a "nurse" or a "CEO") is, you often have to work harder to prove that you are one.
But also, why does the working world have to be competitive rather than collaborative?
To me at least, what's intimidating about applying for a job described as Fog Creek's are isn't that they're competitive -- they don't say "you'll be in a knock-down drag-out competition to beat 100 other candidates". It's that the criteria for acceptance are high -- only those who have an extremely high opinion of their own abilities will consider themselves likely not only to meet those criteria but to be judged by others as meeting those criteria. And many people who are very capable are unlikely to judge themselves so favorably. Women in particular are socialized to underrate our own abilities and conditioned to expect our abilities to be underrated by others, especially in STEM fields.
This is classic horseshoe theory, where extremists on both ends of a spectrum actually wrap around and start to sound the same. In this case they both believe that women are delicate flowers who can't handle the pressure, stress, and competition of the working world like men can.