Well 18% of computer science graduates are female. If we assume that the industry is completely gender-blind then you'd expect 18% of hires to be female, because those are the pool of qualified graduates. Let's assume that both genders have equal talent, on average.
If you apply some preferential treatment to the smaller pool, you do end up with less qualified people getting hired, it's just the way things like that work. Consider that 82% of nursing trainees are female and 18% are male. If you put in a quota system where 50% of the nurses you hired had to be male, then you can bet that a lot of the men they'd have to hire would be low-performing chumps, basically because you burn through the pool of highly talented male applicants much quicker than the bigger female talent pool, and as soon scraping the bottom of the barrel hiring knuckle-dragging neanderthal men. This is just how the numbers work, when you start by assuming that both genders have an equal talent for something, but there are differing sizes of the talent pool.
Also, if you compare 10 years ago with now, the number of female computer science graduates has massively fallen, whilst the number of women in games development roles has massively risen. If the games industry was completely neutral towards gender, then the percentage of female workers should closely track the graduate pool, but it has in fact gone the other way: the games industry employs more women than ever, at a time when there are the LEAST percentage of female graduates with relevant qualifications than any time since 1974.