punctuation - Inconsistency in Strunk and White regarding serial comma

From Strunk and White's The Elements of Style, Chapter 2, Lesson 2:

In a series of three or more terms with a single conjunction, use a
comma after each term except the last

Thus write,

• red, white, and blue


• honest, energetic, but headstrong


• He opened the letter, read it and made a note of its contents.

My question is: Why isn't there a comma after read it in the third example?

Answer

I believe there is a comma after "read it" in the third example in Strunk and White's Elements of Style. I'm looking for a version of the book that does not include the serial comma in that example but haven't found one.

Revision: I found one. It was a PDF copy of an older edition so I couldn't see the publication date. It appears that there was a typo in some versions where the serial comma was left out. Later prints include the serial comma per the style guide's recommendation.

Sorry, another revision. I forgot to give a link to a current copy: http://www.feedbooks.com/book/3697/the-elements-of-style