Certainly not impossible. I would imagine that the factory in China produces goggles for more than just Oakley. But if it were true, I seriously doubt that it would be the same lenses in different shapes.
Anything is possible, alot of brands goggles are made in the same factories. Every brand does not have their own factory that is for sure. Dragon is making a solid product right now, the APX is pretty sick! Check out my website, Action Sport Optics ( google it ), we specialize in optics action sport enthusiasts for skiers, riders, bikers, Mx ers. I have been a lifelong skier/ rider and just trying to live the dream!
Dragon Optics creator used to work for Oakley and in the beginning kind of just branched off Oakley, until his own brand got big. I'm pretty sure he has a close relationship with Oakley, but I doubt Oakley is designing and making their lenses. I read his story somewhere awhile back. I might have to Google it to refresh my memory.