Thank you for saying that. Indeed, from scripture, it cannot be argued otherwise.
I think it is two different words. "You are a pebble, on a stone I shall build my church". The stone being general confession of who He is. That is an interpretation that actually matches the rest of the bible. The idea of Peter being the "head of the church" can't be supported anywhere else.
"He had built His Church on the foundation that was this man [St. Peter]."
Looks like the foundation was the promise to Israel ingrafted by faith, not any man except Christ Jesus.
Rom. 11:24, "For if thou wert cut out of the olive tree which is wild by nature, and wert graffed contrary to nature into a good olive tree: how much more shall these, which be the natural branches, be graffed into their own olive tree?"
So many metaphors, so many theories.