LessWrong posts have staying power; google docs do not.
Great LessWrong posts often stick in people's minds and continue to be reread and shared for years after they are published. It's very rare for great google docs to do so, even if they're initially shared with everyone you care about. And even right after they're written they seem worse at winning hearts and minds. I could speculate about why but here I just want to observe that this seems true. One upshot is that you should often aim for the final output of a project to be a LessWrong post rather than a google doc.
(Also, even if you think you've shared your google doc with everyone who should read it, you probably haven't, in part because some other people should read it in the future.)
(Obviously google docs are better for eliciting input, if you have a good group that will read your docs.)
(Presumably there are some things you can do to make your google docs stick more, including indexing them.)
Relatedly, researchers/writers/bloggers/"the class of people whose theory of change comes from other people reading their writing" should orient significantly towards having their work be read as an important element of their jobs, rather than treat public output as purely "proof of work"/annoying bureaucratic hurdle that distracts them from where the real work is.
Quoting myself, this article is mainly about US's federal funding cut for science may cause universities to create more legible research because other funders value clear communication (such that I don't actually recommend reading the whole thing is helpful for this conversation topic). But there are some relevance:
The choice is not, and has never been, between purity and PR. It is between treating legibility as part of the shared infrastructure that keeps basic and long-term research alive, and leavi
Rich Dad Poor Dad was a book, whose author worked for years to build it up into a brand. That's very different from a Google doc, which is what Zach was contrasting with.