How much is 'that much'? The effect is probably small but what is more important it is not about a moved centre of (a Gaussian) distribution - but rather about a higher threshold usually used for women to pass.

This is of course very much dependant on the distribution shapes and I am too lazy to make a thorough analysis - but:

Let's assume that on average females were 10% more efficient programmers - but with the effort to find one female programmer you can find 10 male programmers. How much more effort do you need to find a 10% better programmer - twice as much as for the average one? Even if it was 8 times harder - then still it would make more sense to look for only men than for only women. Of course the optimal way would be to be unbiased and look for any gender.

Sorry for the late reply, I was away from civilization.

I think that depends on how your hiring process looks like in general. You might, for example do a benevolent (from a certain POV) discrimination and simply start filtering applicants with something like a naive 20-line Python script that matches applicant names against female names from a dictionary and pushes them to the top of your applicant stack, so to speak.

And there are less tangible or directly measurable, but nonetheless important benefits to hiring women for a business: You can get free publicity and marketing if you run a successful women-only shop, there is a significant demand in the liberal media for female success stories and you can ride that wave.