I'd love it if that were true, but the only way to do that on a stock phone is to use Do Not Disturb all the time, set to allow calls from all contacts. Which then blocks ALL other notifications. That's not a practical solution for most people. It also blocks text alerts, as DND also blocks texts from coming through, even from your contacts. (And a lot of people really dislike the idea of blacklisting all calls except contacts, for various reasons, but that's a separate issue.)
If you know otherwise, please detail where to find such settings, because people have been looking for this functionality since the iPhone first came out, and you're the first person I've seen say it's possible. I'd love to know of a non jailbreak solution to this that doesn't mean losing things like calendar alerts, so it can be recommended to those who are resistant to jailbreaking their phones.