I think it simply doesn't matter. The only reason it could have any impact at all is in an incredibly constrained market. Unconstrain the market and they just won't be able to; it wouldn't work.

Also - I don't think it actually affects prices. It's just that they've gotten good at seeking price equilibrium.

“Yes” would’ve been a sufficient answer.

And yet action gets taken about the rent price fixing, but not about actually encouraging more building.

Seattle upzoned huge chunks of the city, allowed ADUs (now two adus are permitted on all lots), and removed single family zoning. All within the past five years.

Last year, Seattle built 20% more houses than the highest of any of the previous ten years. (~13k units) And this year we're 11% above last year, so far.

What about that is not "actually encouraging more building"? I'd say your data might need revising.

It's honestly not that much. I know it looks good when comparing to recent years, but it doesn't look as good when you look at regional numbers (the city limits don't matter much in a housing market) - and the number of ADUs you can build in the entire city in a year is lower than some single new apartment buildings. We aren't keeping up with demand, much less drawing down the likely hundreds of thousands (seriously) of units we need to allow.

That's a different goal post. Seattle is doing things to encourage building housing. Full stop. Which refutes the claim made.

Whether Seattle is building enough housing, or whether the region is doing enough to encourage housing development are separate claims.