"While confidence isn't an issue restricted to just women, it is a more prominent issue for them on average."
This is generally an important thing to consider. Just because a particular issue applies to you or you've seen a similar pattern amongst male colleagues doesn't mean that it isn't a more acute issue for women.
> I'm not convinced that there is widespread sexism in the computer industry, because I've worked alongside and been managed by many fantastic women, and witnessed them advance as quickly as me.
Relying on just the evidence you have directly around you is the same as relying on anecdotes. It's possible you've been lucky and work at a particularly un-sexist companies, but that perhaps the industry as a whole has an issue with sexism.