When MASAL designed the 24th chromosome, it was his intent over a century or two for all of mankind to evolve (or devolve?) into the Onsiras who literally had no mind of their own. Rei and Rome thwarted that plot but did not change the genetics involved. Much of the plot of
The Ark Lords revolved around the fact that the Vuduri on Helome were finding an increasing number of Onsira phenotypes being born.
The Onsiras had their own Overmind. But it was controlled by MASAL when he was alive. After he was gone, their Overmind would not just disappear. And there were more Onsiras being born every day. This is not a situation that could remain stable.
You will find out what happened to the remaining Onsiras in the upcoming novel
Rome's Evolution. The answer may surprise you but you can rest assured that eventually, they are treated humanely.