That is neither the stated reason for affirmative action, nor supported by any evidence that I am aware of. Code is code. Affirmative action is usually framed as a fairness issue, not a pragmatic one.
Be wary of pretending that ideological issues are pragmatic ones to convince people - it tends to backfire when the facts decide not to play ball. As a slightly silly but plausible example, what if it turned out that same-sex software teams consistently wrote better code than mixed sex? You can no longer say "they don't hurt anything". You'd have cornered yourself.
Personally I'm of the view that most ideological arguments can in fact be boiled down to pragmatic ones. But people are not usually fully conscious of the pragmatic observations throughout their lives that have fed into their ideologies, and so - while they sense that they hold their views for a good reason - they often get the reason wrong. Better to admit that you're not sure why you believe something than to make stuff up.
And the problem is that everyone deviating from the party line is strawmanned into "having horrible views" and thus it's perfectly okay to harass them mercilessly and cause them economic harm just for being stupid or whatever.
Today no one can reasonably claim that there was any good by laws prohibiting black and white people from marrying or having children. Yet until recently (say 1970s) this was a very common view! Probably in my southern state it was a view into the 1990s. Claiming that polls show the majority of people oppose AA isn't adequate to argue either direction.