Guy friend you’ve known for a while says would you and him ever go on a date, he asks jokingly?

Guy friend randomly asks me if I would go on a date with him. For context, my girl best friend is his roommate has a crush on him and was hoping that moving in with him would seal the deal for her. I don’t think it’s going anywhere with them. I genuinely was never interested in him as she already told me her intentions with said guy friend.
He’s in front of other people made jokes about me being his ‘girl’ and I just never paid it any serious attention. Just thought he was being a guy and annoying.

He asked me about going on a date when my girl best friend who likes him (his roommate) was sitting right next to him. When I said no she said ‘see told you’ ask if she knew he was going to ask me that. And he said “what you would have a great time” and I said no again and he said “oh well I would definitely change your mind”.

Just want to understand why would he do that when he knows my best friend really likes him.

Guy friend you’ve known for a while says would you and him ever go on a date, he asks jokingly?
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