It isn’t theoretical either - it kills professionals too. [https://en.m.wikipedia.org/wiki/Mann_Gulch_fire], [https://en.m.wikipedia.org/wiki/South_Canyon_Fire], [https://en.m.wikipedia.org/wiki/Dude_fire] for a few examples.
Long story short - never turn your back on a wildfire, and try to stay as far away as possible.