The counterfactual to that claim is nursing. Nursing is a very good job that has a relatively low barrier of entry yet the field is 88% female. The reason for that might be cultural but the reason is certainly self-selection, not discrimination. However, the difference may, in fact, be genetic (hormonal, more likely).

Nursing is the mirror image of programming. If the gender compositions were reversed, the campaigns for STEM would, instead, be for healthcare.

It may not be useful to look at outcomes to determine if opportunities are equal. It may be harder, but looking at opportunities to determine if opportunities are equal is really the only option.