Unless he used some type of video editing he might of inflated the hashrate by playing around with the drivers or bios. I know with AMD cards if you tune them incorrectly, especially the memory straps you will start mining and see crazy high hashrate usually 100% faster.

For example I modded my straps incorrectly and my RX 470 which hashed at 30mhs was showing as 60mhs. The issue is that every share that it found was incorrect or it got massive hardware errors.

So he probably recorded a few seconds without errors and made this video to scam people.