I think a factor may be that men are more motivated to do "manly" sports like surfing and SUP and whatever so they well try it out ... even though they are physically klutzes.
Women, on the other hand, have a life and responsibilities and emotional and personal connections with their friends and families and children (not to mention cleaning up the mess made by men.

)
A woman who is inspired to try SUP even though the boards are ridiculously big and heavy and gay looking, is more likely to be physically competent and more able to deal with the fairly minimal balance and paddling strength requirements.