Well I'd say changing human behavior is harder than changing perceptions. And most of the article (outside of the behavioral bit about the sexism she experienced, which is unfortunately a harder problem) is therefore focused on perceptions, which seems very justifiable given this bit:

"As Dr. Cheryan points out, stereotypes are only partly true, and women who actually take classes in computer science don’t hold the same prejudices as women who get their ideas from pop culture."

So the male nerd culture aspects inside the system aren't as offputting as however the current popular stereotypes make them out to be. Sounds like there are some lower hanging fruit than changing people's desires.

(As to why we'd want to fix it in the first place... I don't know many tech companies right now that are satisfied with the size and depth of the talent pool. Getting more education to more people to become potential candidates could only help with that, and increased demand for a major tends to increase department size, so I don't think it's a zero-sum game with males losing out here. More people with at least a cursory or exploratory level of education in science could eventually lead to better policy around it, etc, too.)