Excellent observation!
They may or may not have, we shall see...
Each fire has its own story...
What may happen, may or may not happen, for some time, or....
Take for example the Tatoosh fire...
http://www.pressreader.com/canada/vancouver-sun/20060912/282033322677131
http://www.osoyoostimes.com/tatoosh-fire-complicates-fight-against-tripod-fire/
Burnt everything except the trunk of the trees.
Years later, all blown over, hence impenetrable, unless your 9ft tall and your legs are 8ft!