Cs and Ts Lines


In a previous comment I was told that writing “my ex left me” in the C line would not be correct as it is actually a thought.
However, in a reply to another question (titled “The C Line”), there was a sentence saying:
“Cs include:
Another person’s action – what they said or did.”

My question is: “my ex left me” is something that my ex did. Why should it be considered a thought?
I could change the C line to “we split/divorced” but I still don’t understand it in the context of the Cs descriptions.

Many thanks