[lloeki]

> those things are not particularly similar. the tree that nobody can hear while it's falling still has a real and measurable impact on its environment in various ways,

Consider a hypothetical game like No Man's Sky. A tree falling on a neighbouring planet has zero impact on the current one the player is standing on.

> something where if if not simulated while nobody was around, the simulation would need to catch up on if an observer ever came near.

That's the wave collapsing part: probabilities become reality.

> this eventually amounts to processing work that is equal or even worse compared to just simulating it in full detail in the first place.

Collapsing treefall probabilities for the small area of a planet the player is due to observe when coming near the area is orders of magnitude less than simulating every single treefall on every planet in real time.

This principle could be equally applied to NPCs, e.g a NPC having a probability to be at this or that place, taking into account a lightcone of causality so that they don't warp from one place to the other.