It’s really not far fetched at all that people would know the details of IW and Endgame off hand. It would’ve been the biggest event in human history (if you exclude the religious). There would be accounts of what happened almost immediately. It would be researched. There’d be websites, articles, journals, magazines, books, etc. dedicated to it. The assassination of Frantz Ferdinand and duchess Sophie weren’t recorded, but we could give you a detailed/step by step account of what happened because it was such a pivotal moment in history, and we had a fraction of the technology we have now. The circumstances of IW/EG would be exponentially bigger.