While I do read the early writers, their words mean no more to me than do current writers in speaking on scriptures. All they tell us is what they think it means, and others may agree or disagree.
Martha speaks these words after Christ tells her "I am the Resurrection"; likewise Nathaniel does so after Christ shows him His omniscience. But Peter confesses without leading questions, as a revealed knowledge from the Father.
Peter, along with the other apostles, was asked a very explicit question..."But who do you say I am?" If that is not a leading question, what is? Peter and the other apostles had heard Jesus say that he is the life (resurrection)on many occasions. But, naturally, they never really took him serious until after he rose from the dead. Peter's response, I believe, was as the Holy Spirit, which is God, moved him to speak.
This is not a very reasonable attitude: St. John Chrysostom read and wrote in the same language in which the scripture was written, lived in a culture that changed little since 1c, and dedicated his life to the study of the scripture and the stewardship of his flock. No current writer can do the same.
The difference is that Peter spoke of Christ being of divine nature in a way that was unique to Christ, while Martha and Nathaniel did not indicate the Jesus was a son of God like no other. There is little in the actual text that says so, but we trust that Christ detected the conviction in Peter that wasn't with Martha (who was, St. John writes, confused) or with Nathaniel (who was startled by Jesus's clairvoyance).