“And when you’re young you want to fit in. Hell, I still want to fit in with certain [sophonts], but as you get older you get a little more discriminating.” - Carrie Fisher -- RecklessPrudence
Even when he didn't have the words for it, Rael knew that he was different from his creche sibs. They were able to do more, work more efficiently. They didn't need as much of the hosts of chemicals they regularly added to Rael's mostly-liquid body. They did not need to use the cheats he used just to perform to specifications.
He learned the wounding dismissal of "stress test version" and "most-failure success". He was the worst product they could make before the genes failed and turned out another Cleaner.
Ayg, the first of the line, was perfection incarnate. The display model. The one they showed off to prospective contract buyers. Those who saw Ayg would likely get the mass-produced others. Trained and run through their paces before they ever saw a non-lab environment.