What it does is make it very clear, that in spite if right wing news, staying in what appears to be dangerous storm may result in your death.What a "mandatory" evacuation order does is absolve the state of liability if you ignore it. They won't come an arrest you for ignoring it, nor will they do some other heinous act against you. Instead, if you choose not to evacuate, you're on your own and you can't blame the state for not warning you that something bad could happen.
Florida does suggest if you stay, you write your name on your arm in permanent maker so they'll know who you were when they find your corpse...