I'd put money on those being a particular N Puget Sound system summer run. We would always call those "swinters." Summer steelhead doing final migration during winter steelhead time. Summer steelhead would enter late June-July 4th on average and migrate through the mainstem and forks and hold until fall. Depending on fall rains, late september/october we would catch quite a few of these summer fish migrating up to the hatchery. By the end of the chum run and into December, the leftovers were those that had spent their fat reserves and were approaching the end of their life cycle. Cool to see those are still around. Can be a fun fish to catch during summer/ early fall.