Erm….. the gender pay gap has been statistically analysed and is a little more complex than you suggest.
While it may be illegal to pay a woman less than a man on an hourly basis for the same role, hours, qualifications etc, the gender pay gap refers to the disparity of overall earning and progression of women because they are currently disproportionately affected by the fact that child rearing and other caring responsibilities hinders them over the course of their working life.
Of course women can choose not to have children, but that does rather screw up society in general, as eventually we’ll just run out of people.
If you think about it, the current economic climate makes it nigh on impossible to avoid both parents working, preferably full time.
Quite often women pay a disproportionately high percentage of their earnings in childcare costs, so saving for their future is impacted.Of course the idea is that women keep working through the years when childcare is necessary in order to keep their place on the career ladder etc. In practise, outsourced child care can be hit and miss for a variety of reasons, and workplaces may only have so much patience when plugging the gap left by female employees to whom the majority of childcare falls.
Nothing in this thread is as black and white as you would like. Because humans and society are messy, complex creatures affected by culture, bias, and a dog eat dog capitalist society.
A gender pay gap, or if you prefer, disadvantage, does exist, whether you like it or not.