Mac OS X has had smartcard support for a long time. They started removing it a few "updates" ago, but the support was still there. CACKey specifically added missing bits as Apple removed them. This latest release probably features their replacement architecture.

I haven't seen what is needed to make CACKey work on the latest release of the Apple's OS since I don't use it, someone else works on packaging that up.

Yep I realize it's been there, but (as you mentioned) keeping it updated has been ignored by Apple long time and turned into a community effort. Sierra brought a significant overhaul.