If your too exceptional for the CHL at 19, you should be in the NHL. There are always things you can work on to improve. This isn't like Strome or Marner who absolutely tore up their league for 2 consecutive seasons. And even then, Strome still has things he can easily focus on improving at a lower level.
Is the CHL ideal? Maybe not. But, if Steel isn't good enough to make the Ducks outright, there are probably things he can focus on improving at the CHL level. You start draining top talent from the CHL eventually, it starts to diminish its value as a developmental league. Steel benefits by being able to go against guys who would have gotten this exemptional status such as Provorov, Barzal, Juulsen, Fleury, Sanheim etc over the years, and now kids like Woo, the Foote's, Addison, etc benefit by playing against Steel.
I'd say its very rare for a kid to be above playing in the CHL, but not good enough to play top 9 minutes in the NHL.