What does "mandatory evacuation" really mean?

I mean, I assume they don’t go door-to-door and physically drag the stragglers out.

Does it just mean “Leave. Now. or you get no help from us whatsoever”?

I was camping in Maryland on the shore years ago when a bad storm occurred. There was a “mandatory evacuation” with park rangers using bullhorns. I asked if we had to leave and he said, “it’s your ass”. We stayed and had a thrilling (scary) ride of our lives.

Already active thread.

Basically, yes. It means that if you stay, and then get in trouble later, nobody will be coming to your rescue. At least, not until the disaster has passed and they have nothing better to do.