Nah, looks to me like they're just controlling what they're allowing others to display directly on their platform. You can still support Pebble, you can still advertise that you support Pebble, you just have to advertise that on a different platform than Apple's. Sounds reasonable, if a bit inconvenient.
Users find apps for their iPhone on the App Store. There are no other app stores for the iPhone. Users do not visit an app's web page before they install it.
Users will not find anything when they search the app store for e.g. "navigation app with pebble support". Users will not see Pebble support listed as a feature when they compare two apps.
Developers know from the above that they won't gain any appreciable number of users by adding Pebble support.
In that light I don't see much difference between banning mentioning a feature and banning the feature itself.
It is a tool for controlling the behavior of both users and developers by using their control of an unrelated platform.