It's all well and good to pretend that this is the case, but it isn't. Most jobs involve some obvious measure of progress. Especially under the umbrella of "service." Women disproportionately choose these jobs: nurses, servers, etc. Women are more educated, hell the last time I went to the doctor there was a resident, a nurse, and a doctor, all three where women.

There could be some jobs where it's hard to measure progress, like quality assurance, but these jobs have been looked at with ire by management for so long it's an old wives tale at this point.

What is likely more true, is that productivity varies between employees somewhat, and perhaps there are 2x employees. But, measuring relative productivity is much, much harder.