Yes, I did try that. It does not fix it.
I believe it's because Spritekit is so similar to Cocos2d that it creates a long list of conflicts in naming. It's my opinion that when Apple decided to create their 2d game engine, they basically copied what they saw in Cocos2d.
The bigger issue is that objectively, GameKit (i.e., GameCenter) should not depend upon SpriteKit, which is a competitor to 3rd parties like Cocos2d, Unity3d, etc. It's probably an oversight by Apple, but it makes them look like they are forcing developers to use Spritekit. In the past adding the GameCenter functionality WAS independent.
I take it as yet another sign that Cocos2d is being forced out. I could be wrong, but it was a good platform so kind of sad how things end up going.
I only use Cocos2d to update my legacy apps, but I have quite a few of these and so it probably means switching to a different platform (entire rewrite of 4 years of work). On that note, I don't like either Spritekit or Swift and will probably do everything in Unity3d from here on.
I still need to safely comment out the #include Spritekit.h from Gamekit header file (which is write protected)...any suggestions would be appreciated.