What stops a celebrity’s dating partner from revealing their relationship?

A K-Pop singer made a song about her toxic ex…only she didn’t reveal his name. She only referred him as “the ex.” Well, what’s stopping whoever this guy is from simply going on social media and saying “Hey my name is (insert ex) and I dated (insert Kpop star). Here are some pictures of us at a restaurant as proof.” Come to think of it, the biggest Kpop group has 4 members who are over 30 years old…and zero dating news ever. How is this even possible? What stops their partner from revealing the relationship to the public?