Yeah, the rod did nothing. I also think it would be odd to assume that this thing is single-phase.
As other have suggested, compaction is potentially needed to transport waste from the deeper parts. But there are several security considerations of just ejecting trash as-is from a high security area. I imagine a trash compactor is also a way to destroy the trash to prevent the old “spy tosses a data device into the prisoner cell block waste chute and have his allies follow the death star to pick it up during ejection”.
As other have suggested, compaction is potentially needed to transport waste from the deeper parts. But there are several security considerations of just ejecting trash as-is from a high security area. I imagine a trash compactor is also a way to destroy the trash to prevent the old “spy tosses a data device into the prisoner cell block waste chute and have his allies follow the death star to pick it up during ejection”.