Obviously it is important to be skeptical when controlling for job title.

If there were an institutional bias against women tech workers, one way it could manifest is by women receiving less recognition and promotions, or being hired in to lower positions with the same skills and experience. Which would mean they might typically have a lower job title than the equivalent male worker, so controlling for job title could hide the bias.

I'm not saying this is or isn't the case, but it is a rather blatant possibility that isn't addressed by what is seeming like a naive study.