You’ve never embellished a story to make it a bit better down the pub? People exaggerate and people lie all the time. I’m guilty of it and I’m sure most people on here can admit to it as well as you.
Even if John didn’t, do you not think it’s possible that over the last 2000 years the story could’ve evolved and expanded? Especially in a time when reading and writing was very rare and most stories would’ve been word of mouth.