Citation, Documentation of Sources

Q. Hi—A question about CMOS citations with two examples:

(1) Leigh Wood, “University Learners of Mathematics,” in Research in Mathematics Education in Australasia 2004–2007 (Rotterdam: Sense, 2008), 73–98.

(2) Leigh Wood and Ian Solomonides, “Different Disciplines, Different Transitions,” Mathematics Education Research Journal 20, no. 2 (2008): 117–34.

Why does (1), a book chapter, use a comma before the page numbers, whereas (2), a journal article, use a colon? Is it just for historical reasons? It seems a little idiosyncratic for no apparent reason.

A. I suspect it’s because journal citations are typically more complex: that is, they can have numbers for volumes, issues, series, parts, columns, et cetera, in addition to page numbers. Journal citations are also likely to be read by someone whose first language is different from that of the citation. Thus the use of a colon right before the page number is helpful as a signal to someone trying to navigate a complex citation, perhaps in another language.

Or it might just be one of those things the original writers of CMOS overlooked and no one has ever questioned.

[This answer relies on the 17th edition of CMOS (2017) unless otherwise noted.]