It's more subtle than that. Better paying jobs are more likely to go to men, so a women with similar qualifications and experience is likely, on average, to earn less than a man. It's easy to fix too, just make the jobs more accessible to female candidates. Obviously you still hire the best candidate, it's not about favouritism.
For example, a lot of well paying jobs are found through networking. If most of your current employees are male and network with other males, you are less likely to get female candidates applying or head hunted. All you need to do to correct that is to make an effort to network with women, and maybe ask some of the women in your company to put the word out. It benefits you because you have a wider pool of talent to pick from. It's actually dumb not to do it.
There is also bias at the hiring stage that can be eliminated. Some managers don't want to hire women because they worry that they will go on maternity leave or quit completely if they get pregnant. That one is harder to deal with, but does again exclude good candidates and diversity from the company.
How would that help tech companies to hire female tech talent that does not exist?
How do you suggest we get around the problem of companies trying to hire equally in a field that women dispite heavy positive discrimination on their behalf choose not to enter?