It’s not grammar and it’s not a correction. The phrase “I could care less” has only one meaning and that meaning is “I don’t care”. It is being used correctly.
Does it? I decode it instantly and understand the meaning just like I know what a "fishbowl" is. There is no "decoding" or even nonsensical input in this case.
You are just being stubborn and trying to adhere to an outdated standard. Upgrade or get replaced.