There's a typo, I meant lowering (not lower) particles, and I'm using the term particle vaguely to cover that they're geometry instances.
The amount of particles in the starfield hack is arbitrarily chosen against hardware performance in a regular grid of all things, and the updates to the simulation are dependent on performance - from what I can see in the video - with particles further from camera simulated slower to stay within performance.
Astrobot's sponge situation is completely different given the camera, the main character animation model, character movement and fx all change , as does the environmental fx as the water is used and wears off so can't be optimised by less particles or slower simulation in the background.