Apple approves Microsoft's Health app for use with the Microsoft Band...Kindle Reader...Office for iOS...
You can't compare Pebble to Microsoft. Microsoft has much more market power. Pages and Numbers notwithstanding, Apple needs Microsoft to continue to support Office applications on the Mac. Also, Microsoft has invested in Apple in the past; the companies have a relationship.
We'll see what happens with Pebble. I wouldn't presume to call it either way.