Meaning that the runtime got an mapping from the internal animation engine to the API that is exposed to the public. Internally the engine can animate everything and the mentioned map exposes the attributes Hype chooses to expose. Potentially nearly every attribute you can see in the timeline properties could be public. Only thing as internally the properties use shortcuts the map would increase the size of the runtime but a few new basics shouldn’t be a problem. At least in my personal opinion as a regular user/citizen!