https://www.seattletimes.com/business/real-estate/seattle-re...
Humans are really good at crafting narratives explaining complex and uncertain reality. However, just because something sounds superficialy plausible, doesn't mean it is true: it is usually easy to craft an alternative theory, just as plausible as the one at hand.
For example, the narrative of Prop 13 being the root of all California's housing problem very much depends on exactly how much it affects the decision making. It could be a lot, it could be a little, but without knowing exactly (or at least approximately), we're simply in the dark. Maybe it's not Prop 13, but environmental activists running amok? Maybe it's a cartel in the construction industry colluding to keep the construction prices up? Without putting numbers on these, you can't tell which of these has significant impact, and which is irrelevant.
Sure, but without any numbers, this is simply a just-so story. House prices in Seattle metro have shot through the roof in past 5-6 years, despite Seattle not having Prop 13 law. If house prices can demonstrably go up a lot in a place with no Prop 13-like law, but otherwise rather similar to California when it comes to attitudes towards what kind of houses are allowed to be built, it stands to reason that Prop 13 is unlikely to be main factor in dire California's housing situation.