Well, the argument comes from the fact that the most gender equal countries still have very high level of men and women assuming traditional gender roles.
https://en.wikipedia.org/wiki/Hjernevask
And we are not sure what that is.
https://en.wikipedia.org/wiki/Hjernevask
And we are not sure what that is.
Gender roles is what you would expect from a species that developed distinct genders. For example, the simple fact that hormone levels are different between genders, should strongly imply differences in behaviour which should bleed into day to day choices. The fact that one gender specializes with birth, while the other with insemination would strongly imply this difference would in some way segregate genders within a developing culture, and so on.
So I cannot imagine how the "social construction theory" could possibly be correct.