You're right! Although I bet the general public wouldn't have made it a hit if she had released it. People are happy to hear Ed Sheeran objectifying a woman's body, but they wouldn't accept it if it was Rihanna singing about a man.
She definitely seems like the kinda person who only records vocals for songs she's almost definitely going to release, which is probably also why we get mediocre tracks like 'Pose' on her albums...