While I technically agree with this, it is absolute nonsense from a user point of view. As the provider of an important host system, you might want to consider allowing people to list supported platforms in order to make it possible for the user to see which apps he can use with the equipment he has.
It might be right from an objective point of view but it's a plain out dick-ish behaviour towards user friendly app management aka the user itself.
Yep. If I was an iPhone user and just bought a Pebble, I'd go to the App Store and search for "Pebble" to see what apps I could buy that work with my Pebble. It's the same thing I did when I got a Moto 360. I went to the Play Store and searched for "Android Wear" to find apps that make use of it. If I'd gotten a Pebble, I would've done the same thing.
It sucks for the developers of iOS apps that are meant to integrate with Pebble (or other similar devices). I assume this means you can't create an iOS app whose sole purpose is doing something with a Pebble watch since otherwise there's no real way to describe it in the app store (not one that would make for easy discoverability at least).
It might be right from an objective point of view but it's a plain out dick-ish behaviour towards user friendly app management aka the user itself.