Not true for slower moving animals like koalas, and even fast animals can be overcome by firestorms raging all about them.
Humans in their vehicles can be and have been overtaken by fire storms. They are not slow moving things. A local firechief said that even if he had 200 fire crews out there fighting the wildfires, the only difference it would have made was that there would have been lots of dead firemen to add to the list of the casualties.