Simulation can proceed in logical time but animation is necessarily tied to wall clock time in order to be perceived as smooth and consistent by a human viewer.
In that case, animation belongs to the same category as audio — it exists outside the simulation state.
But I’m not 100% that’s even true; in the context of replay, I imagine it’d be more appropriately part of the sim for it to scrub properly.
In the context of networked games with client-side prediction, I think it’d probably be key frames tied to logical time and intermediate frames tied to wallclock
