(0.9 x 30%) / 11% means that California has a homeless rate 2.5X the rest of America. That's not impossible, in fact it seems surprisingly low. California is the land of $3000/month rent. A very significant proportion of the population can't pay that.
Finland isn't responsible for all the homeless from Sweden and Denmark. It had a number that makes sense based on it's population and resources, therefore it was able to solve it.
I think housing prices does make the homeless problem worse, but it didn't create it. Good climate and numerous public services did.