pope_meat is right -- even in the age of unsolicited dick pics, mostly women were interested in participating in this project. Men were very hesitant. Also, more models of women than men worked out, since photogrammetry is very sensitive to movement. Any body parts further from the core where more subjected to movement from heartbeats and breaths. Vulvas are closer to the body and thus less affected.
Women have more need for information on our genitals. Our genitals are hidden from view and we get less natural exposure to what they look like, what's normal, how they compare to others, etc.
Also "If you're wondering why we have the collection of models we have, see our model diversity statement for more details. " https://wearebeautiful.info/docs/model-diversity