Ah, it's really complicated. My hunch is that that's part of it but not the full story. I think it takes a mix of factors to make a person self-define as a 'computer geek' by high school, which is -- imo -- a point at which the gender divide in college is already determined. Various efforts blend the categories later on, but they're fighting against the categories that already exist by HS-age.
Some factors:
1a. being socially allowed to love computers, OR 1b. not caring what's socially allowed <- me
2. obsessiveness (3rd-grade me would happily play videogames for 12 hours straight if allowed. Or read, legos, etc. Other kids would, like, learn everything about airplanes.)
3. not caring very much about socializing. 'play over people', if you will.
4. being intelligent
5. having 'growth mindset', the idea that you could go learn something if you wanted to. (I think I got this from books and RPGs and from not being demoralized early on.)
6. not caring very much about pop culture (in my case, because I didn't know about it. sports and music weren't on my radar).
7. being competitive: wanting to learn cool things to, basically, seem cool to other nerdy kids.
8. an innate desire to build things
I would characterize (1b) and (2) and (3) together as being, basically, the 'autism spectrum' angle, which is (I perceive) more prevalent in boys, and I think that's where the main difference comes from.
I think what the social effect you mention exists, but it might come before these categories -- ie, from a young age I was constructed so as to not care what was socially allowed and to want to obsessively play, and so I was basically destined to be obsessed with computers. I don't know how much is nature vs. nurture though.
I also think that on average girls are less (7) naturally competitive and (8) naturally motivated to build things (citation needed), but that very well could be a social effect also.
I think lots of people of any gender have their (5) 'growth mindset' squashed from a young ago.
I also think lots of boys have almost everything on the list except for '(8) desire to build things', so instead of learning to make games, they get really good at Halo and play every day in college, or whatever.
I also think that by the time college rolls around, these categories are all smeared together, and people end up going into tech or STEM (and I guess I mean specifically CS/Math/Physics) for lots of reasons. I'm only trying to describe the commonalities across the nerdy kids in HS.
Disclaimer: all of this is hunches and is from ~2000-2008 and is probably not correct or true and if it was it probably isn't anymore.