Whilst targeting individual groups can certainly lead to inequalities there is the problem of tailoring ads to an audience. One way a company may wish to make their ads more appealing is by showing relatable people in adverts.
If a company is running two variations of the same job advert, one featuring women and one featuring men, distributing coverage across the two variations evenly, then is there still an issue? I would argue not, yet introducing a non-gender targeting rule would make this impossible to do and could in fact have the opposite affect to what was desired by the regulation.