The link is to the glossary of the WHO. While they accurately define sex as the state of being a biological male or female, and gender as socially constructed roles which vary over time and cultures, they then go on to list how equity and discrimination is all based on gender, not sex.
If an organisation of the size, reach and influence of the WHO do not accept that women are discriminated against and abused based on their sex as opposed to their conformance to stereotypical roles, then we have even more work to do than I imagined.
www.who.int/gender-equity-rights/knowledge/glossary/en/