How does 'actual biological sex' manifest itself socially? How is it referenced culturally, by systems in day-to-day life if not by a certificate?
Really good question, and I'm glad you asked.
'Actual biological sex' manifests socially and is it referenced culturally for most women hundreds of times daily since early childhood and all women more often than it should in all the ways that women are undervalued, underpaid and underrepresented in life, and men (including trans-identifying men who claim to be women) are not:
• Pay
• Domestic work
• Seniority
• Representation
• Healthcare
• Social status
And that's just in western so-called liberal society. In Afghanistan "actual biological sex" is culturally manifested by women not being taught to read or write, or move outside the house unaccompanied by an "actual biological man" for fear of being beaten and imprisoned, and sexually assaulted and raped.
"Actual biological women", unlike you, don't have the option to throw off the shrouds of their sex-based opression - a shroud that nobody ever asked them if they wanted to wear before landing it on them.