Why does matter whether it is simulated efficiently? What if each Planck time or frame takes a huge amount of "real" time to simulate, we would not know it.
Think of a Pixar render farm that takes hours to render one frame, the characters inside would not know that, their world unfolds in real time to them.
Think of a Pixar render farm that takes hours to render one frame, the characters inside would not know that, their world unfolds in real time to them.