It's not that the orchestra was suddenly 50% women, it was after going to a preliminary round blind audition 50% more women were selected than when the auditioner could see the performer and was hence judging on a mixture of performance and unconscious or conscious bias.
So why would less than 25% of undergrads in IT be women?
You posit some genetic gender distinction observable from birth. If you are suggesting somehow that it somehow means women are less capable than men at IT and is the major reason as such you'll need a lot more support for this assumption you've jumped too.
Studies have already found biases by teachers push girls away from math:
http://www.nber.org/papers/w20909
I've personally seen bias against math with my girls. My eldest daughter accelerated a year in math in elementary school. We had to force the school to test her which she passed easily. When she did they sat us down and asked us, "
Do you really want to do this? It could damage her socially and make it harder for her to get into college because she'll get a lower GPA in HS because she'll have to take harder math classes."
She's gotten A's every year.
Now it's possible the school just has a thing against gifted kids and not necessarily against girls but when my coworkers son (in a different school but same district) was doing well in the school asked her if they could test him for acceleration.
Further more our school put out a kids t-shirt which was supposed to say the kids were like 4 different superheroes. All 4 were male superheroes. When my wife asked the principal why they couldn't have put a single female superhero on the shirt she said, "The Boys wouldn't like it." No problem in the principals mind with girls have boy superheroes only a problem with boys wearing a shirt with a girl superhero. That's a gender
bias.
Women are on the receiving end of gender biases that push them away from STEM jobs.
The good news is world class organizations know they get better performance if they have diverse groups so are pushing back against those biases.