It does help and is helping. Here's an article published this week in Berkeley about how a modest building boom has stabilized and lowered rents in existing buildings, after rents doubled in the 2010s.
If you look at the trend for all Bay Area cities over a similar period [1], you'll see Berkeley is pretty much in line with the overall trend.
Now you can argue that's because of greatly increased development, but I don't think that applies to SF (or SJ) and it doesn't match the Berkeley timeline anyway.
Yeah, the specific contribution here is tracking a stable cohort of existing housing, not the entire market, to show the effect of new construction on the price of older housing.
https://www.berkeleyside.org/2025/05/01/berkeley-housing-ren...
Note: I developed the data used in the article.