I don't think so, because the rates are not immutable, and you're discounting causation going the other way. If the women who are hired are treated well (which would require their employers to undergo some training), the rate of women attaining software education is likely to rise. "Downstream" likely has a strong effect on "upstream".
First, I don't think they claim a 50/50 split. I guess there's still room for improvement even before hitting the applicant pool limitation (I have seen it, too, BTW, when we hired; the number of women applying is higher than their representation in startups).
Second, it's also very possible that there is a local, fast, feedback loop. I think women would be more attracted to companies that already employ a higher number of women, and are known for a hospitable working environment, so it's likely those companies will receive a higher share of women applicants.
