You'd be surprised (or maybe you wouldn't) how many K/S fans use that footnote as "proof" that Gene intended K/S as canon.
Let's see: Oh, right, that's an out-and-out confession. But yeah, there's unfortunately no shortage of people in the world who, when faced with facts that unambiguously disprove their convictions, will twist, reinterpret, and contort those facts until they can take them as proof instead. For instance, in the direct converse of this, there are still Legend of Korra viewers who refuse to accept that Korra and Asami are lovers now, even though the creators of the show have confirmed it (and illustrated it, though not nearly as graphically as many fan artists have). Still, I can't help but notice that Kirk said he found his best gratification in woman -- which could easily be taken to imply that he's tried the alternative(s). Not with Spock, most likely, but with somebody.
Seen this? The Roddenberry Footnote Then there's Gene's mumbled "the affection was sufficient" response to Marshak and Culbreath's prompting in Shatner: Where No Man... I'm guessing this is what Justman and Solow talked about -- that Gene often just said whatever the people he was talking to wanted to hear. Furthermore, Nimoy flat-out contradicted him on the "I can't live without you" business.
Just bumping this because Gerrold recently went into more detail about his thoughts about them. He doesn't name names, but is fairly obvious about it in a recent Facebook post concerning the "Gay Sulu Kerfuffle of 2016" One of these women, I'll call her M, had written a doctoral-length thesis explaining the planet Vulcan and especially Spock. She sent a copy to Gene Roddenberry, who appreciatively replied, "Gosh, you've sure done a lot of typing. I applaud your enthusiasm." She had the letter sealed in plastic, put it in the first page of her extraordinarily large binder of documents and waved it under the nose of any unwary fan who got too close. "See, Gene has authorized me to be the expert on Spock." Her partner in Grime, I'll call her C, accosted me in the con suite of the very first Star Trek convention I ever attended and said, conspiratorially, "Let me tell you what you Star Trek writers don't understand about Kirk and Spock...." Okay, I'm arrogant. I was trained by Gene Roddenberry, Gene L. Coon, Dorothy Fontana, two editions of the Writer/Director's Guide, with additional input from Bill Shatner and Leonard Nimoy -- so I figured I probably knew as much about the characters of Kirk and Spock as anyone else who'd written dialog for them. Before I could stop her, C backed me into a corner, lowered her voice to a whisper and said, "Kirk secretly wants to be homosexually raped by Spock..." and In the several years that followed, M&C fully earned the obligatory epithet of FUBBA-WUBBA by the way they treated other fans. They assumed ownership of the entire K/S phenomenon and proceeded to chase any fan holding a divergent view out of fandom. They did it in the social media that predated the internet -- the fanzine, they did it by creating hoax identities that abused and degraded anyone they chose as an enemy. At one point, they even told a 16 year old gay man that he could not write K/S stories because he didn't understand male homosexuality. and They did eventually co-write a Star Trek novel. One chapter of it was distinctly pornographic. That was the chapter they left out when the book was published, but which they privately distributed. To me, that was deliberately unprofessional -- a kind of deliberate subversion of the Trek universe. (That their book was published was their claim to additional credibility in fandom.) etc. But again, he doesn't know much about what led to their fading from the franchise. Sounds like there may have been burned bridges.
link to the deleted chapter? I have enjoyed their novels. They are bizarre, but entertaining and distinct in style. I loved their characterization for the female Romulan commander. She was strong and dominant. And as a gay men who very often felt unrepresented in sci fi, the slash subtext was welcome. But that whole bit about Kirk wanting Spock to rape him is pretty disturbing. It does kind of make sense in the context of their writing as the Phoenix books' antagonist is obsessed with Kirk submitting to him, and their emphasis on Vulcan and Romulan physical superiority did leave Kirk coming off as somewhat fragile by comparison. Still, as someone who enjoyed their writing and even appreciated the somewhat back door inclusion of diversity via subtext, it's still a shame to hear that they allegedly treated other fans badly. Telling a teenage gay boy he couldn't write slash because he didn't understand homosexuality is bizarre and offensive. I can imagine they themselves faced a lot of prejudice from some fans because of the subtext in their writing. It's disappointing that they turned that same attitude back towards people. I would try to keep in mind that we're not getting their side of the story. It doesn't sound pretty but I try not to judge hastily.