I've read this yesterday, and it's kinda weird.
The community says they've debunked his cheating and needed months to do so, going through every possible seed to determine that the dungeon in the video doesn't exist and the very important and early item drop is not naturally possible.
But apparently no one of them has read the video description, which explicitly stated that a) it's a spliced run and b) he manipulated the item to drop as early as possible. Could've spared them a lot of effort.
...done in 27 segments appended to one file...
...cut down the time almost in half and it's due to even more luck manipulation...
...The most important thing is that I manipulated Naj's Puzzler to drop from the earliest monster possible...
Note that I took these from an archived shot of the video in 2014.
https://web.archive.org/web/20140314230825/www.youtube.com/watch?v=dW8XorD9RwI
I took the quotes from the HTML file, though, because the drop-down didn't work. The description is the same as today.