The statement 'Sex and gender are different' is supported by multiple reliable sources that distinguish sex as biological attributes and gender as psychosocial and cultural constructs.
Sex and gender are different

Pacific Center for Sex and Society - Sex and Gender are Different
Source: hawaii.edu
Key Evidence
PMC article states clear differentiation between sex (biological) and gender (social/cultural) is necessary for research equity.
pmc.ncbi.nlm.nih.govpmc.ncbi.nlm.nih.govDifferentiating sex and gender in health research to achieve gender equity
AMA Journal of Ethics article defines sex as biological traits and gender as psychosocial self-perceptions and societal roles.
journalofethics.ama-assn.orgjournalofethics.ama-assn.orgSex, Gender, and Why the Differences Matter
Simply Psychology explains gender as socially constructed roles differing from biological sex.
simplypsychology.orgsimplypsychology.orgWhat Is The Difference Between Sex and Gender
What the Evidence Shows
The majority of the sources clearly differentiate between sex and gender, emphasizing that sex typically refers to biological characteristics such as chromosomes, hormones, and reproductive anatomy, while gender encompasses the social roles, behaviors, identities, and expectations culturally associated with being male, female, or other identities.
(PMC) highlights the importance of distinguishing sex and gender in health research to effectively address gender equity, indicating that these terms are not interchangeable.pmc.ncbi.nlm.nih.govpmc.ncbi.nlm.nih.govDifferentiating sex and gender in health research to achieve gender equity
(American Medical Association Journal of Ethics) explains that gender is a complex psychosocial continuum involving self-perceptions and societal expectations, whereas sex is a biological classification.journalofethics.ama-assn.orgjournalofethics.ama-assn.orgSex, Gender, and Why the Differences Matter
(Simply Psychology) discusses how gender roles are socially constructed and can vary across cultures and time, while sex is based on biological factors present at birth.simplypsychology.orgsimplypsychology.orgWhat Is The Difference Between Sex and Gender
(Reddit r/asktransgender) provides a community perspective reinforcing that sex relates to biological attributes and gender to internal identity.reddit.comreddit.comr/asktransgender on Reddit: Are sex and gender different?
Some sources (e.g., WebMD) acknowledge that definitions can be murky or vary among individuals but still maintain the distinction between sex and gender.webmd.comwebmd.comWhat’s the Difference Between Sex and Gender?
Overall, the evidence from diverse academic, medical, and social perspectives consistently supports the claim that sex and gender are distinct concepts. This distinction is widely accepted in contemporary health research, psychology, and social sciences.