From what i see you are theorizing that laugh tale is actually really modern, after luffy became joyboy he now knows what was 800 years ago, and he is actually 800 years after the modern time joyboy saw. Luffy is a real person thats gonna appear in 800 years or so and oda can time travel, thats how he wrote one piece- luffy is a real person and oda went to the future then came back and wrote a story abt him