I didn't say they were thinking
consciously of property rights. I have been in discussions with
women who were trying to find a way to signal to their boss or someone else who was potential trouble that "No, I am not up for a romantic relationship with you" and trying to figure out how to do so without offending. They often try to do so by emphasizing to the man "I have a boyfriend." I always tell them that is the
wrong approach because it signals to potentially predatory men that she is perfectly willing to go along with being some man's property and all he has to do is find some way to claim her as his own. That's the wrong signal for a woman to send if she really wants a career. She needs to find a polite way to deflect his attentions without saying "It's cuz I
belong to someone else right now." Some men take that as a challenge, as "come get me, big boy." So it is not a good way to avoid trouble.
If women want to compete with men and not just be their toys, they need to exercise agency and own their decisions that "No, I am not up for a relationship with you. Because I say so, not because of some other man's property rights over me." If a woman says "I would get with you if I weren't with someone else" she needs to really and truly mean that. It shouldn't be a polite fiction. Such polite fictions tend to lead to worse trouble than the one they thought they were trying to cleverly sidestep.