The Metal feature set tables list features for each GPU family. I assumed that if a feature is present in a family, then it must be supported for the GPUs in the family, otherwise what's the point of specifying families? But I see exceptions to this assumption, so I'm confused how to make sense of this table.
For example, I assumed that features listed for the Metal 3 family must be supported on all GPUs in the Metal 3 family. The Metal 3 family includes A13, which is the Apple 6 family. But I see features available for Metal 3 not available for Apple 6. (Could it be that a feature available for A13 is not available for Apple 6?) For example, see "SIMD-scoped reduction operations."