UE4 4.13 supports Shader Model 5 features for Mac OS X 10.11 El Capitan where the Metal API does not support tessellation, so there’s still no support on Mac in 4.13.
After macOS 10.12 Sierra is available later this year, we will add support in a future engine release. I can’t promise exactly which release at this time but the intent is to get it out this year if possible.