Agreed. From what I've read [1], the syntax rules and semantic rules take up about 40 pages with the rest of the book being "introduction, exposition, core material, appendices and index".
[1] http://mythryl.org/my-Mythryl_is_not_just_a_bag_of_features_... (go to the middle of the page or search for "pages")
While that is certainly nice, I suspect it makes it hard to really compare based on just pagecount. I doubt prose and such a formal definition like that are equally dense.