Pure speculation on my part but I would think the indigenous chinooks would have had a similar life history as most red fleshed chinook stocks, that is 1-2 years in the river before smolting. You can bet on one thing, there will be no data, other than anecdotal, to verify much about these fish. Most people don't even know they existed.
I fished them in the late 60's and up until the mid 70's ... they were never abundant but perseverance would get you into a few every year. Catching was dependant on the freshet, as back then the C-V actually did get one, and because of the high water, landing these super charged fish was difficult. The largest I saw was a fish I estimated to be 35 lbs, hooked in the Boulder Hole. You can guess the result
We started fishing for them in June, early July and although I and a few buddies caught a few in August, we pretty much considered it done at that time.
Did they go into Chilliwack Lake, stage until sexually mature, then drop back and spawn? Who knows ... The staging in lakes seems to be a water temperature related strategy (like Cultus and Harrison sockeye); the upper Chilliwack is always cold so I can't see why these indigenous fish would do that ...
They were magnificent fish and I hope a few are still around, and I wish DFO back in the day had spent a bit more time and effort in enhancing that run, rather than fish entirely unsuited for the C-V. My $.02