[@Akayaofthemoon][@ianzerep][@Pathfinder]
I don't think that the Diamonds would do that. For one, I sincerely believe that Yellow Diamond is about as smart/logical/materialistic as a 3rd grader, and two, what Akaya+ianzerep(do you have something else we could call you?) said.
Example: If they could control how gems came out, Emeralds would be a lot less insane, but still diverse in power.