“social construct” doesn’t mean “fake”. it means our understanding of reality is shaped by the way our culture makes sense of the world. reality shapes us, we shape reality.
Baseball, pizza delivery, and bicameral legislature are all social constructs
They also all exist. They just didn't come from space or grow on trees. They can't be derived under Zermelo–Fraenkel set theory with axiom of choice
They're still real, like all social constructs
Essentially, it means that said thing is simply an accord subject to change as the needs of society call for adaptation. The social construct of binary gender or heteronormativity doesn't hold up to the longstanding history of humanity or the present realities of who people actually are in life.
The book Sapiens explains this clearly
Modern life is built upon shared myths like money, religion, nations, and even human rights. These shared beliefs give our lives meaning and allow us to cooperate on a large scale, but they are ultimately human constructs, not objective truths.
