I don't think the title is true. It is just an UX thing and I believe an improvement. After an attempt to run an unsigned app, it will appear explicitly listed

I don't think the title is true. It is just an UX thing and I believe an improvement. After an attempt to run an unsigned app, it will appear explicitly listed on that dialog and you can click a button to explicitly allow it. So instead of allowing all apps from "anywhere", you allow them on one by one basis. At least this is what happened to me with one unsigned app (after installing 10.12 DP on a clean partition).