What ? I think you read it backwards 🙂
The feature introduced with iOS7 is notification sync which (if used fully) should sync the same set of notifications across multiple devices.
So if I swipe away a new email alert on iphone, the same alert on the iPad should disappear as well.
This does not happen for iCloud. What you are seing is the server side implementation for Exchange, etc where when you read an email, its marked read on server side thus pushing the same state to other devices using the same email (Nothing to do with the notification sync)