Poor ocean conditions should affect HOR and NOR fish nearly equally. Otherwise that could reasonably explain the fall Chinook, coho, and steelhead differences. I don't know what explains the Chinook and coho discrepancies, but my hunch is that 2016 wasn't the first season that the number of hatchery summer steelhead smolts was significantly less than the programmed number.

On average it's not unreasonable that natural production salmon and steelhead would experience a higher smolt to adult survival rate than their hatchery counterparts.