True, most players won't make these demands, and bow out. Friends or even reasonably polite players will then say, "No, don't do that. We'd rather have you at the table and scrap our nautical theme. There's a ton of other cool ideas out there that we can all enjoy." Then said player will try and tell group not to change their plans just for them, and table will say, it's fine, we don't mind, etc.
I'm hoping this is a more common example then person swooping in, making demands...
The guide is just a way to sort stuff out ahead of time, isn't it? And it's probably not going to be super common that there be no rats or deserts. It's not going to bring games crashing down cause there's too many things on the no-go list.
Well, no, it isn't. I wish it was. If it had have been, I would have liked it better. But the guide borrowed a lot of ideas from discussions about consent in a sexual relationship, which might be perfectly fine discussions of consent in a sexual relationship, but which are problematic in the context of a most social role-play.
For example, in a sexual relationship, we would like it if consent could be withdrawn at any point and for any reason, and when it was we'd like that to be prioritized over pretty much anything else in order to avoid rape. In a sexual act, it makes perfect sense for everyone to have a full veto over continuing the process.
But the problem is that this doesn't always provide a good model for mutuality in a social role-playing group. Consent in a group is usually about consensus, and has some give and take, and usually involves discussions - all the thing that you imagine in your head when you imagine how this ought to play out. But that doesn't seem to be the actual statement of the text, which as I said was borrowed from ideas about sexual consent.
While run time objections to content that comes up are of course reasonable (and I'd argue normal and maybe preferable in most cases to airing everything out ahead of time), it's not necessarily reasonable to expect that if something comes up during play that we just stop everything right away with no discussion, no explanation, and no negotiation about how to proceed in order to get the game going. Maybe some objections actually are like that, but most of them just don't involve activities that are nearly as unsafe or traumatic or potentially dangerous as all of that, and when people start hearing people talking about social RPGs as if they are usually that unsafe, traumatic and potentially dangerous they really start wondering what people are trying to communicate and if that really is how we want to publicly represent our hobby.
And people shouldn't necessarily expect that they can hold a full veto over the game, beyond simply walking away from the game,. But, in this thread, you can find people arguing that if someone was made to walk away from the game, because the group couldn't accommodate them, that that was a monstrous act. Maybe in some imaginary cases it was, but not for the majority that actually come up.
And other people suggested that while a full veto over some things might be reasonable, suggesting that a full veto could be used about anything - which while reasonable for two people in a sexual act - not only wasn't reasonable for social gaming, but would be likely to encourage dysfunctional play in practice and increase acrimony rather than harmony and consensus.
So in short, no, most certainly the guide is not about just sorting things out ahead of time.