The traditional viewpoint is that women are on average better than men verbally. Or at least higher in quantity.
Why males have so greatly outperformed females over the centuries in quality is a very good question. I don’t have any facile answers.
Some of it, without doubt, has especially in the past been due to prejudice. But it seems unlikely that all of the differential can be assigned to this factor.
If women are upset about this differential, the cure is for them to sit down and write great literature. Not to stand up mediocre women writers of yesterday and today and claim that their works were really great literature ignored only because they were women.
It may also be the nature of what they are measuring and how. They may be measuring some component of what it takes to write great literature or be a great speaker rather than the whole range of abilities required. In other words, they may have performed a valid experiment but mischaracterized the result.