It's not fiction, that's hyperbole, but there are factors other than gender by itself that accounts for a lot of the remaining disparity between men and women's pay. Taking a career break to have children, historical 'steering' of women away from STEM subjects in education, some apparent natural tendency for many women to avoid such subjects even when they have a free choice, a tendency for women to not challenge their compensation or push for raises compared to men, women's tendency to avoid overtime compared to men which can affect their advancement prospects. There are a lot of factors that come down to personal choice, and women often make different choices from men.
Nevertheless even controlling for all this there is a remaining gap of a few percent at least, which varies greatly depending on the industrial sector and also by region. Since this thread is about the EU, it's reverent to point out that the gap is particularly high in some EU countries.
https://www.epi.org/publication/what-is-the-gender-pay-gap-a...