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)

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.