That number seems unbelievably high. LAHSA for example found that only 15% of homeless individuals have a substance abuse disorder.

https://www.lahsa.org/documents?id=3422-2019-greater-los-ang...

You just missed the distinction. Talk to people who work with “street people” and they will tell you almost all either suffer from mental illness or addiction. This is not the same as people who are housing insecure.

Good point I did miss that. They also included mentally ill with substance abuse disorders.

As other commenters have mentioned, people living on the street don't comprise the majority of unhoused people. It does seem like California has a higher overall percentage of "unsheltered unhoused" people among the unhoused. But e.g. here in NYC the vast majority of unhoused people move in and out of the (largely corrupt, poorly maintained, highly restrictive) shelter system, and a only small percentage live on the street or in the subway.