Chairman of Worldwide Studios Shawn Layden has confirmed that Death Stranding "actually exists" and that it is indeed playable. Unfortunately, even though Layden played it, he couldn't explain what the game was about.
“…It's up and running,” Shawn Layden confirmed to Telegraph. “It’s been aided tremendously after Kojima-San decided to co-opt the Decima [graphics] engine from Guerrilla [that powered Horizon Zero Dawn]. And, gosh, that really gave him a leg up to get up and running and test it and have some prototype levels running. I couldn’t explain to you what the game is…”
The PlayStation executive went on to detail that it was as revolutionary as Kojima promises "and more."