“The discourse on the Eucharist in John 6 relates it to the Ascension (John 6:63)”
I think it was a general teaching to the assembled Jews in the synagogue (John 6:59), “These things said he in the synagogue, as he taught in Capernaum.” The explanation of what he meant by the idiom “so I ate up every word he said” is what he gave to the disciples.
A year before the last supper he was telling his audience that everything he said and did was life to them. That’s why John could say later in the Gospel (John 20:30-31) “And many other signs truly did Jesus in the presence of his disciples, which are not written in this book: But these are written, that ye might believe that Jesus is the Christ, the Son of God; and that believing ye might have life through his name.”
John did not say “eating his flesh...drinking his blood” but used the words of Jesus in John 6 “It is the spirit that quickeneth; the flesh profiteth nothing: the words that I speak unto you, they are spirit, and they are life.”
“John did not say “eating his flesh...drinking his blood” but used the words of Jesus in John 6”
To the contrary, In John 6:54, “Whoever eats my flesh and drinks my blood has eternal life, and I will raise him on the last day”
John put extra emphasis on the word “eat” by not using the classical Greek verb of human eating, but that of animal eating “munch, gnaw”. He was making it clear he meant literally eating.
No, because if the meaning was idiomatic, no commotion over it would have ensued, and the Last Supper would not have repeated the essential of giving His body and blood to eat linking it to the Passion.