Probably has “green” Al Gore toilets that pretend to flush with not enough water.
You’re right about flow. Triple the flow and most of the problems will go away.
Ship heads flush using saltwater firemain so there is no reason to worry about the amount of water used. However, you may be on the right track here. Did they screw things up trying out some new system when the old system worked well enough? Of all ships I was on (and a couple over 40 years old), we never had every head on the ship go down at the same time.