Did an Oxford-comma error lead the press to overstate British gains at the Battle of Loos?

Debate has long raged about use of the Oxford comma (aka the serial comma). This troubling comma has its own Twitter feed, and it can be crucial for interpreting laws. [Update March 19, 2017: Here's a more recent example of a legal case involving the controversial comma.]

I was raised in accordance with The Canadian Style, which includes the Government's of Canada's recommendation not to bother with the serial comma unless it is required for resolving an ambiguity. Some have called any wider use of the serial comma unCanadian. Indeed, it is said to be unAustralian and unBritish, too (despite its Oxford pedigree). It is reputed to be an American thing.

I found an antecedent of the Government of Canada's advice in an Ontario high-school textbook from the 1920s. The book is called High-School English Composition. ^{(H. W. Irwin and J. F. van Every [Toronto: The Copp Clark Company, 1921, rpt. 1929])} The authors say that the serial comma should be used only when necessary. To exemplify its capacity to alter one's meaning, they give this example:

During the Great War, when the British troops were engaged in a critical struggle with the Germans for the possession of Hill 70, General French sent the following message to England: 'We captured the western outskirts of Bulluch [sic., should be Hulluch], the village of Loos, and the mining works around it and Hill 70.' By an error, the message was made to read: 'We captured the western outskirts of [H]ulluch, the village of Loos, and the mining works around it, and Hill 70.' The insertion of the comma after 'it' conveyed the impression that Hill 70 had been captured. In consequence, public celebrations and rejoicings were held in all parts of the country. (pp. 199-200)

It's difficult to find much by way of corroboration for this tale, and the putative celebrations sound far-fetched. Still, the sentence that implies the taking of Hill 70 (and close re-phrasings of it) did appear in newspapers on Sept. 27, 1915 and shortly thereafter. On Oct. 16, 1915, the New York Times (p. 2) quotes a passage from the British Daily News under the headline, 'War Office Official Gives Evasive Answers When Questioned', according to which the Under Secretary for War had tried to clarify matters by saying:

There has been a misunderstanding on this point. The message from Sir John French, which was published in the papers of Sept. 27, stated that we had captured the western outskirts of Hulluch village, Loos and the mining works around it and Hill 70. This was been [sic.] read to mean that Hill 70 had been taken. If the words were correctly read it would be seen that the capture only of the mining works around Hill 70 was claimed.