” “Mandatory evacuation” means exactly that - you are on your own.” So Your are saying mandatory does not mean you are compelled by law to leave?
Interesting read here: https://www.americanbar.org/publications/law_practice_today_home/law_practice_today_archive/april11/fight_or_flight_on_enforcing_mandatory_evacuations.html
As the link you cite identifies (thanks, BTW), the enforcement part of the equation is variable by state. Some states have this as a criminal offense (such as CA). Other states, such as LA, give tacit permission for forced evacuations by case law (due to issues during Katrina).
Also from the link, a mandatory evacuation order also can be used to make additional resources available for evacuees, and to make the decision for those incapable of making their own decision.
It’s a delicate balance, where not having the governmental prerogative of “ordering” evacuations means that the government cannot relieve itself of the need to stand up police and rescue in peril of their own lives. But to give such an order too much force means that individuals cede more than is necessary to their government.
The actual impact of such a mandatory order varies by state, but it appears this is the strongest level of warning that anyone who stays behind will be bereft of governmental rescue.