If you’re going to make some sort of guarantee or have a marketing message, it’s very important that you say what you mean (and vice versa). When consumers go out of their way to pick your brand based on your message, you want to make sure that they get what they think they’re getting. If a customer thinks you mean one thing, and finds out it isn’t so, they won’t just be confused, they’ll be a little peeved – which can undo all the effort you’ve spent marketing the message in the first place.