Indeed, but He was naturally present with them at the time. The Institution actually occurred at the Last Supper with the commandment given the holy Apostles, "do it". The discourse on the Eucharist in John 6 relates it to the Ascension (John 6:63), as it is at that time that the Eucharistic Presence of Christ became a necessity for us.
“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.”