In the US "Could care less" is the equivalent to the British expression "Couldn't care less". The intention and meaning is the same. So the original comment did mean to say what they said.

My point was that what may look like a mistake or a contradiction is just cultural development of natural language.

Another example is the British expression "It would be cheap at half the price"

One example to illustrate: when talking about dying, Americans would kick the bucket, Poles would kick the calendar, French would break the pipe, Germans would drop the spoon, and the Spanish would pull the leather. But they all would be referring to the US's trust among its allies.