True, but that fact is no license to take anything Jesus said and because for some reason you don't like it say, "gotta be metaphor". The "drinking" part in John 4 is a take off from the fact that He was given water to drink; but the life giving water is of course Baptism because He did give us that, and life-giving it is. Gate and vine metaphors are self-evidently metaphors because they come in the course of the same passage. There is no commandment to drink water and there is no commandment to do anything about gates and vines. As to body and blood, the metaphorical interpretation flies int he face of the text itself, and indeed thare its a commandment to "do this" and a discourse that it is "food indeed".
No one says that all of the gospel is literal, but all of the gospel is inerrant as written. When a metaphore is offered, the inspired author made sure no sect in 16c could come alone and credibly pretend that they obey the scripture.
As written by whom? The original authors? The current NIV? You have made an excellent point that if one does not interpret through the eyes of the consensus patrum, then that interpretation can support, why, any heresy that can be imagined by men, and influenced by the lord of this world.