I say, if Jesus’ hearers were not ready for his “real point,” and if that “real point” was faith, then why did Jesus go on at such length earlier in the chapter (6:29-47) about having faith in him?
In John 2, as your friend rightly says, Jesus didn’t wish to speak openly of his Resurrection to faithless men, so he used a “shocking metaphor” to obscure his real point and to “shake them up” at the same time. But in John 6 Jesus spoke quite openly about having faith in him. He laid those cards right on the table. Why would he then seek to muddle what he already had stated so plainly?
Jesus used figurative language for one of two reasons: to illumine, or to obscure. When he sought to illumine, he sometimes appended plain explanations to his metaphors (especially if he had been misunderstood), but nowhere did he do what your friend thinks he did here: follow a clear exposition with puzzling metaphors on the same point. There would be no reason to do so. If he meant to be obscure, he would not have been so plain to start with; if he meant to be clear, he would not have muddied the waters with obscure metaphors.