There are separate rankings for emulated runs versus original hardware runs. He (allegedly) submitted something as an original hardware run that was run off of an emulator.

Using an emulator, you can alter the game's performance, change the speed, set a save state and revert to it if you fail at something, etc. and then play it back and record that. There's no way to know if that's what happened, but the video he submitted does not show that it was recorded using original hardware.