I read a pretty in-depth article recently written by an expert who said that, like with anything else, there are several quality levels of DLC treatment available to industry. He is guessing from what he's seen that Apple appears to have used a premium treatment on the Apple Watch, and it likely uses Tungsten in the process, making it exceptionally resistant to damage. The Garmin probably uses a lesser DLC method. Still strong, but not nearly as good as the AW. Sounds like this is the case based on your experience.