Probably about a LOT of things.
But what is the single best way to ensure your dominance over your people? Make them feel powerless.
Peridot is living proof. She was told that all Peridots of her generation can’t have any abilities like a regular gem, and was immediately given her limb enhancers. Once she has those, why try to use abilities? You are obviously not functional or they wouldn’t give you these right?
It’s such a subtle thing but…such a small thing could EASILY change vast aspects of Homeworld Culture if it were found out.
What else would they be lying about?