Why change a "good thing"? Because the agency is required to consider the supposed ecological consequences of the hatchery. The goal of management now is "do no harm" to the wild stock. It is not "provide a fishery". A fishery is a secondary goal to wild fish protection.

As to the timing thing, I mostly worked with winters and had only some contacts with the Kalama but I recall that back in the 70s there was, even then, a big push of summers that arrived at K Falls in late summer/fall. If they were holding in the lower river or not, I don't know.

Also, have water temps in the Kalama changed? The Deschutes in Oregon, until the recent recovery plans were put in operation and warmed the lower river, used to host many over-summer stocks from Idaho. Summer in the cool Deschutes and then go home when the mainstem cooled.