The essential feature of this bill is that the rate of increase allowed is well above long-term market trends. This is qualitatively different from a rent control policy that aims to keep rents perpetually below market rate.
The "housing crunch" is a very general term; the specific symptom addressed by this bill is drastic increases of rent on, for example, a change of ownership of a building. See https://www.latimes.com/california/story/2019-09-05/how-cali..., which has actual references to advocates of the bill.
> Supporters of the measure have pitched it as a way to prevent sudden increases in rents at levels that could drive people from their homes as the state experiences a surge in housing costs.
Assembly members in favor of the bill talked about "providing certainty", not about keeping prices low.
Also "some fictional landlord spiking rent for fictional renters"? The article I linked describes sudden increases to rents during changes in local housing markets:
> In Boyle Heights, apartments without rent controls saw rents increase from a median $1,200 a month to $1,700 between 2016 and 2017.
The OP references this area:
> Sandra Zamora, a 27-year-old preschool teacher, lives in a one-bedroom apartment in Menlo Park, Calif., a short drive from Facebook’s expanding headquarters. A year ago, Ms. Zamora’s building got a new owner, and the rent jumped to $1,900 from $1,100, a rise of over 70 percent. Most of her neighbors left. Ms. Zamora stayed, adding a roommate to the 600-square-foot space and taking a weekend job as a barista.
This rent control bill would force the new owner to spread that increase over several years.