Sorry, the writer is correctly using a common, somewhat illogical idiom.

"I could care less" has been around for a very long time to mean, "I don't care".

I first started hearing it in New York City in the early 80s, used satirically. At the time, "Like I could care less" and "Ask me if I care" were also popular. They eventually drifted out of the picture, but "I could care less" stayed.

I don't personally use it much in speech, not at all in text, and when I do I use a broad sarcastic tone to make it clear, but it is part of my vocabulary.

Idioms don't literally mean what they say.