That's the problem with anything that's true 99% of the time. People start to believe it's true 100% of the time. That's why your ex didn't expect this 'SLA',

That's the problem with anything that's true 99% of the time. People start to believe it's true 100% of the time. That's why your ex didn't expect this 'SLA', because most of the time messages arrive practically immediately. And that's why most people don't expect Facebook to block non-spam, non-offensive content, because most of the time they don't.