I am not an "old timer" but I will share what I have learned about the blackmouth. Resisent Chinook (blackmouth) have allways existed in the inland waters. In the past(20-30 years ago) they were primarily make up of wild fish that had a natural deviation from their normal migration habits. As time has gone on and wild fish numbers have declined, the WDFW looked for a way to suplement the population of blackmouth to maintain the fishery. They found that by holding the juvinile Chinook in the hatchery holding ponds for an extra year, it broke the instincts of those fish to go out to sea.
This does not mean that if left alone the fish would not migrate back to their rivers of origin.
As far as their impact on hatcher fish, they ARE hatchery fish. If they eat each other, fine.
The WDFW has somehow determined that the impact on the small wild population is insignificant but the reduction in the length of the winter fishery is a result of concern that wild blackmouth are being caught. I expect that when the fin clipping of hatchery Chinook becomes more wide spread that we will see selective regulations in effect and possibly a full winter season