Your theory here is that there is a one-way relationship between supply and demand, but that's not the case. Increasing supply pushed down on prices, but that can increase demand, sustaining high prices.

That's especially important during a boom (or bubble, depending on your view). With the rise in prices, many companies are finally looking at putting offices elsewhere, or allowing more remote work. Building more housing would have only dropped prices if the pace of building outstripped the tech sector's ability to create jobs, which is prodigious. At a recent SF CTO conference, a number of speakers talked up non-SF options, something I wasn't hearing 5-10 years ago.

As to who likes the status quo, you ignore that "more building" here mostly means "tear down existing buildings and build bigger ones". That is a gain for the people moving in to the eventual new units. But it's a clear loss for the people forced to move, and a disruption of existing communities.

I have yet to meet a SF "build more" advocate so committed that they tore down their own home and replaced it more units.