Guy becomes distant when I flirt with other guys?

I’ve heard that if a guy (who you aren’t with) catches another guy flirting with you, then that’ll turn him into a more “competitive” state, because men enjoy that. Is this true? This guy I work with, who I think may like me, seems to be the opposite. He becomes distant when I show certain guys attention. What does this mean?
Guy becomes distant when I flirt with other guys?
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