You're right about the rent on the low end. These things take time. Seattle, like many other cities, under built due to poor zoning policies for years and years. This deficit doesn't get fixed overnight (or in a year).
It'll happen though if current building trends continue.
I may not be representative, but the average rent dropping doesn't mean anything to someone renting a bottom 10%-cost unit.
Average rent may very well be dropping - but the average renter is not someone who lives right on the margin of having a home, and sleeping on a park bench.