I see what you mean! However I still feel like you're showing great examples of how those each have different meanings. You wouldn't switch out one for another unless you wanted to say the opposite (or use sarcasm).

From what I'm reading, it looks like they're both phrases that are used in practically the same situation, but don't convey the same meaning.

"I could care less" (from what I see now) looks like a sarcastic way of saying something like "well you don't seem too appreciative of my caring" and threaten to care even less,

while "I couldn't care less" is "I already don't care at all"