When the whole fuzz about gender discrimination started, Microsoft and Google published numbers, claiming women got the same pay at the same positions as men. Knowing there's discrimination from personal experience/feeling, I theorized, that women are discriminated in a different way: they don't receive promotions.
Under otherwise similar circumstances having children does not feel to be enough to explain why of 100 women hired in tech on professional roles less are promoted to higher positions, than of 100 men. That trend is (at least anecdotally for me) observable even before people become parents.
This "Bamboo Ceiling" shows the same effect for another potentially discriminated group of people.
The neat thing about this form of discrimination is that you can claim to be fixing "the pipeline" all you want and you can still maintain the discrimination, because the leak is after the pipeline. The dominant group isn't threatened by competition if they fund efforts to increase the number of underrepresented groups in grade school or college STEM education, as long as those college graduates aren't later competing for senior jobs on a level playing field.
But what is their incentive to "maintain" discrimination. Even under a charitable interpretation, it seems to imply there is a group at the top which actively hates women and wants to suppress their influence? Maybe there is, Google is pretty scary and is in bed with the government https://www.opensecrets.org/lobby/clientsum.php?id=D00006782..., but I think it would be good to dissect that statement to see what it points to.
Check out the literature on "implicit bias". While there are problems in some social sciences, this particular research area has a lot of high-quality reproduced studies. Of course, it is only the start of the conversation and there are many caveats, but I believe it will address your comment.
But they do research that should be repeatable and thus it doesn't matter.
Unless you think they have implicit bias.