I am listening to the audiobook version of The Rise and Fall of the Third Reich by William L. Shirer and one thing that caught my attention was when the author claims that the myth of the 'stab in the back' had two origins.

For those who don't know, the 'stabbed in the back' myth states that Germany lost WWI not due to 'defeat on the field' but rather 'betrayal on the home front', and is usually tied in with anti-semitic conspiracy theories.

One origin that Shirer suggests is that a German military officer was having a conversation with several foreign officers and after one particularly long-winded tirade an English officer responded by attempting to summarize it in just a few words, resulting in 'so, you were stabbed in the back?' The phrase was so well liked that the German officer repeated it everywhere and the name stuck.

The other being that a book by another English officer came out and that the German press published a series of reviews which completely misrepresented it. While the term stabbed in the back wasn't used here, the implicit idea was the same. The issue here (and this is the point that I'm interested in) is that those who liked the myth didn't care to actually read the book that supposedly proved their thesis. That they continued to believe despite the author publicly writing about articles attempting to correct the record. It just became part of the accepted narrative of what happened.

Is the latter origin of the 'stabbed in the back' myth true?