The linked book is 3.9 MB. That you would have to reload every time a new post was appended to the end. This is a terrible counterexample.
I'm not sure I understand the connection? My argument was that War and Peace sounds like an incredibly big thing to load because it took people a long time to read it in high school, but it's actually pretty simple, structure-wise, when compared to a discussion forum.
Even Chrome on my i7 doesn't instantly respond when loading those Gutenburg URLs.