Only after they had eaten is it made clear that in addition to this being a miracle, it was also a model for their future partaking of the sacrament. In verse 5, Jesus notes that there will be those who will have the power to break bread and bless it. Of course, we know that this is a power that would have been given to the twelve, but the implications are that there would be even more who could perform that sacrament.
Before the distribution of the wine, it was made clear that there was a sacred context in which these common food items became symbols. They were no longer just food to assuage hunger or thirst, but the symbols that indicated that spiritual hunger and thirst were fulfilled in the mission of Jesus, the Christ.