That can be true, and was true in some cases. But in many cases in Santa Rosa there was no wall of fire. There were unburned trees and even unburned houses in the middle of burned houses. That suggests mostly windblown embers (your first thought). Most of the roofs were not shake, but asphalt shingle, probably class A, probably did not catch. But the houses had many entry points at vents, soffits, siding joints. Many houses that burned had indented corners while a plain square house next to it did not burn.
“There were unburned trees and even unburned houses in the middle of burned houses.”
That caught my eye as well.
In the 1993 Laguna Beach Fire one house on a street of maybe 50 survived. It was built with fire resistance in mind.
IIRC the eaves were minimal and boxed so that superheated air wouldn’t collect under them. The attic vents were an ember-proof design. There was no exposed wood that could catch fire and lead back into the main structure.
Some of this would be very easy to incorporate into a house. Even to retrofit. California should encourage it in existing homes and require it in new construction. Insurance companies should encourage it.
Most homeowners won’t know about this construction in order to ask for it, but architects and insurers and builders should. It’s terrible to see people lose their homes and even die when a way to prevent it should be available at a reasonable cost.