A lot of these seem to be ambiguous. "Let's have lunch sometime" followed by some form of actual commitment (phone number, "does next friday work for you", etc) might mean what they literally said. But if it's used to end the conversation... Yeah, you're not getting lunch.

"Let's get lunch tomorrow/this week/some actual date!"

Took me a while to realize this actually works, as a born and raised American.

“works” as in “gets the other person to leave me alone”?

“works” as in “the meaning of the phrase depends on whether timing is indicated.”