GribbleGrunger
Dreams in Digital
A playable montage of scenes from the previous Uncharted games and new scenes (such as whatever events led up to Sam's arrest), seamlessly flowing into each-other, all created from scratch in Uncharted 4's engine, ending in Nathan Drake waking up at his work desk.
As I've said before, those choices we see are played out in real time. We get to play the memory which is why the camera pans up and then down so quickly. They cut that out so they didn't give it away. Believe.