In fact, it doesn’t take a scholar to see this. Let’s say for example John’s story of the cleansing of the Temple. Were John just reporting the ‘facts’, we should expect the story to simply go on like this:
In the temple he found those who were selling oxen and sheep and pigeons, and the money-changers sitting there.
And making a whip of cords, he drove them all out of the temple, with the sheep and oxen. And he poured out the coins of the money-changers and overturned their tables. And he told those who sold the pigeons, “Take these things away; do not make my Father’s house a house of trade.”
So the Jews said to him, “What sign do you show us for doing these things?”
Jesus answered them, “Destroy this temple, and in three days I will raise it up.”
The Jews then said, “It has taken forty-six years to build this temple, and will you raise it up in three days?”
No fuss - just a dry report about ‘what happened’. Something that’ll make modern Westerners happy. But that’s not how John writes. Instead:
In the temple he found those who were selling oxen and sheep and pigeons, and the money-changers sitting there.
And making a whip of cords, he drove them all out of the temple, with the sheep and oxen. And he poured out the coins of the money-changers and overturned their tables.
And he told those who sold the pigeons, “Take these things away; do not make my Father’s house a house of trade.”
His disciples remembered that it was written, “Zeal for your house will consume me.”
So the Jews said to him, “What sign do you show us for doing these things?”
Jesus answered them, “Destroy this temple, and in three days I will raise it up.”
The Jews then said, “It has taken forty-six years to build this temple, and will you raise it up in three days?”
But he was speaking about the temple of his body. When therefore he was raised from the dead, his disciples remembered that he had said this, and they believed the Scripture and the word that Jesus had spoken.
Did Jesus really make those long speeches? Did He really speak those discourses as written word-for-word
historically? I’ll be frank. Without any time machine or video footage, we can’t 100% say “yes.” For all we know, the speeches could have been a great deal shorter historically.

But then again, we could say that John’s purpose is not so much to jot down what Jesus would have actually said word-for-word as if he’s writing a script or news report, but
the deeper meaning behind those words that John (thanks to the Holy Spirit) had now realized. Just because John would not have transcribed those discourses as Jesus spoke them historically that doesn’t make the contents “false;” if anything, now that the deeper meaning behind them is revealed I’d say it makes them more ‘true’.
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This is part of a post I made a while ago. This might be relevant in a way to the topic.
The human mind
doesn’t work like a video recorder that plays back an exact replica of events remembered, contrary to popular belief. Memories are actually reconstructed like a puzzle rather than played back like a video each time we recall them. And inevitably there’s going to be some ‘rearrangement’ along the way; some bits are lost, and some ‘foreign’ bits - which properly don’t ‘belong’ there - will be added. In fact, as per some studies, you’re lucky if even 50% of your memories actually represent exactly what happened. Some people will use expressions like, “I remember clearly that…” or “I remember it just like yesterday,” but those actually aren’t completely true. Inevitably one’s ‘memory’ of a given event is just our mind’s reconstruction of bits and pieces, filtered through our current state. Because our view of the world is constantly changing everyday, our minds don’t reconstruct those memories perfectly. Some people have exceptional memories and can ‘reconstruct’ things better than others, but even their recollections fall short of 100%.
There’s even the idea of our brains implanting 'false memories. That may kinda sound distressing to some people, but that’s just how our brain works; nothing wrong there, since there’s nothing we can do.
In other words, do not blame John if his memory of Jesus is ‘contaminated’ / ‘enriched’ (depending on your POV) with the knowledge and revelation that he had received during all those years in between. He’s not a robot nor a tape recorder; he was a living human being.