They very well may have been stuck by this point. There are a lot of canyons in this area that have one road in/out and if that gets cut off, you're stuck. I've heard they were telling people to get out of their cars and walk out in some places.
It's a good reminder that if they tell you to evacuate, that's the time to leave. Not time to start getting ready or give it another 30 minutes to see what happens.
Good point. Yeah, not sure we flatlanders with our grid of roads aways appreciate that the only way out might have been cut off miles from where you are at and before you know you need to leave.