The beloved disciple vs Peter

The order of the gospels were written has been traditionally accepted as Mark, Matthew, Luke, John.

As time passed, they had the opportunity to examine the scriptures more closely as Jesus had taught them, and as the Bereans did, to see that Jesus fulfilled the hidden prophecies therein.

Each book in the order they were written demonstrates a deeper understanding of the hidden things exemplified in the treatment of John the Baptist. John as the last author, was able to link the circumstances of the life of Christ to the most hidden prophecies. The book of Revelation is a masterpiece of riddle based on the metaphoric prophecies of the Old Testament.

So the details 'revealed' in John are not necessarily because he knew the details at the time he observed them (some details possibly even collected afterward as the apostles shared their memories, such as the future of Peter) but he was able to tie the details to OT prophesies because of the greater amount of time he had to study the scriptures and reflect upon the detail. He records them because they have meaning when tied to the OT.

If we read the gospels as sermon notes (just the reminders of what Jesus did) and presume the audience knew the OT, we can tie the details to OT prophecies. Peter was a type of Christ being that he was a rock and Jesus was the rock.

The rock that was split in the OT is a picture of the cross as God is divided Father from Son. Peter as a type of Christ must also be 'split' from Jesus as he denied him three times. Why three times? because the rock was split three times. So John believed while Peter had not yet been reconciled with Jesus. The detail tells us more about Peter than the beloved disciple. This information is necessary to properly understand Peter's reconciliation on the beach.