I have to disagree. Maybe this is too much detail, but I want to wade into each one of the points of the post you reference:
> A core theme is that Billy Mitchell is an asshole, one who doesn’t even deign to spend time in the same location as Steve Wiebe and won’t even come in to eat lunch at the same table as him. In fact, Billy came in and paid for lunch.
One, the entire plotline about Doris setting a Q-Bert record was included to show some of the selfless things Billy does.
Two, Steve Sanders makes it clear in the restaurant scene that Billy "didn't want anything to do with Steve" and that he came "unexpectedly and uninvitedly." This is Billy's best friend saying this. The fact that Billy comped everyone's meal does not contradict these facts -- besides, it was his own restaurant.
Is Billy an a-hole? That's hard to say. But if the reporting in this ArsTechnica article is correct, Billy is at least a cheater and liar.
> Billy denies Steve the satisfaction of playing one-on-one on Donkey Kong. They’d played Donkey Kong one-on-one a year before the documentary was filmed at a previous championship.
The reason Steve wanted to play Billy publicly wasn't to play once and be done with it, it was to repeatedly show Twin Galaxy doubters that Steve was a consistently better player than Billy. If they wouldn't give Steve his score at least he wanted to show as many people as possible that he could play at or above Billy's level. I think Steve would have loved to play Billy 20 times because no one believed he was a million-point Donkey Player. Could the film have added, "We played once but I'd still like to play him again in front of everyone so the world can believe me?" Sure. But it's not some falsehood that compromises the film.
> It seems like Steve Wiebe finally gets a chance to top Billy and that same day, a videotape arrives and Billy tops Wiebe. Steve Wiebe already had the top spot in Donkey Kong, having achieved the record before the documentary started.
The videotape that Billy sends in has a suspicious glitch. The videotape was a copy and the original was sent in with no glitch.
The point of this article is that Billy's videotape was indeed a fraud, so this "no glitch" defense doesn't hold up so well. Plus the bigger issue is that they denied the validity of Steve's tapes but blindly accepted Billy's tapes, an unfair double standard.
> Two representatives of Twin Galaxies arcade forced their way into Steve’s garage and looted the machine. Two members of the same social scene as Twin Galaxies and Steve were let into his garage by his grandmother, and asked Steve for permission to photograph the circuit board.
The movie makes it pretty clear what happened was disputed and tried to present both sides of the story. But at no point does the movie claim they "forced" their way in or somehow broke into Steve's garage.
> A number of insiders constantly appraised Billy on what was going on at the competition and took suggestions from him. Multiple times, the conversations being shown from both sides are not the same conversation.
What's the proof? Billy has made claims of selective editing but the producers deny them: https://film.avclub.com/the-king-of-kong-continued-donkey-ko...
Instead, this author says he is bitter that the King of Kong coopted his own efforts, now he can't make a documentary on a similar subject because people are afraid of being made out to be the bad guy. I quote, "And by doing this, he f* me, too. Doors that were open to me and my production are slammed shut."
If you have other arguments why KoK is a "seriously flawed work" then let's hear them, but the above points are not compelling, IMHO.
(I have no affiliation with the filmmakers, just a fan)