"Let's have lunch sometime" - Yeah, when I say that I genuinely mean it. It does NOT mean "I don't want to see you again." to me.
"Thanks for reminding me" - Again, I genuinely mean that when I say it. NOT "Stop bugging me!".
This list is not supposed to reflect how people actually talk with each other. It's just a made-up sarcastic list, put together for the sake of humor. That can be a fun thing, as long as we don't mistake for an useful phrase book that tries to describe what people actually say and mean.