After looking over this game several times, something doesn't seem right. Engine analysis of this game reveals that Alexander only made one inaccuracy in the entire game!
I'm higher that 1460, and I know for a fact that I regularly make inaccuracies in my games. OK, it was a simul, and maybe Alexander played well and got lucky because Nakamura wasn't playing 1v1 and made some bad moves. But a 1460 playing that well seems suspicious to me. The only moves I disagree with in the entire game were 7... a6 & 13... Na5, but they weren't bad moves - I just wouldn't have played them myself personally.
https://www.chess.com/news/view/nakamura-visits-south-african-chess-events
https://www.youtube.com/watch?v=vJJbOtDSZHc
What do you think?