Why do people fake their personalities?

Why would someone fake their interests that define them?

I was talking to a guy in my class and he told me that he is really into rock metal music. He knew that I listened to it a lot so I asked him his favourite band. His face flustered. He started stuttering. I was so confused. He said Imagine Dragons and I laughed and left . But I think he just wanted to make conversation but why would he lead with that?

Also I was at a book convention last week with some of my friends. We started talking about songs and artists. A girl told the group that she loves The Smiths. My other friend asked her about her favourite song. She didn't say anything and it was wierd asf.