Diversity reporting is a no-win scenario.
There are plenty of good reasons why the resulting figure calculated as an average seems to imply something it doesn't.
a) many women like flexible jobs with lower hours because they actually care about their families
b) In general, flexible jobs are in lower-paying job categories
c) women often take a career break to have families, which means they don't climb the corporate ladder to the higher-paying posts
Even if you do the break-down and show you aren't discriminating, someone will summarise it to make you look bad and create a story out of nothing.