Oh come on. The dude skipped 99.9% of the content. I fail to see anything resembling an accomplishment there. (That's not bullying, that's an observation.)
Whatever floats his boat though.
Speedruns are about getting to the end of the game. Not 100% said game.
That said, there are many categories: 'any % runs' and '100% runs' and 'glitchless runs' because, of course, a 100% run will take longer than a run where you glitch to the ending credits in 5 minutes.
But they are all valid speedruns.