Something I suspected was the case but hadn't heard the term - or seen any research on.
In SF the battle is over what will happen in the next 5 to 10 years. In that context it is politically dangerous to support market rate "luxury" housing. On a longer timeline this is the only thing that will make a serious dent.
Instead they are pushing for 25% of all developments to be affordable housing, which will retard the whole market and worsen the problem.