The flaw in your assessment is that here in fla the number of teslas on the road is far less than what you see in your part of the world, the amount of SpCs is adequate for this event.
As long as there is power the SpC units should remain operational.
Ft Myers has been problematic for awhile
Normally, the cost to the driver of a busy/down Supercharger is a long wait at the supercharger, or a detour to a slow charger.
When evacuating before a hurricane, the cost goes way up, as you run the risk of being stranded (or delayed) in some area that is itself in the route of the hurricane.
Why would anyone risk that?
[Not to mention the fact that, without redundancy, there is a chance that, on the drive back, a supercharger you need will have been damaged by the storm or rendered inaccessible. By contrast, it's pretty much a given that some gas stations will still be around as long as there is power in an area. Plus, you can carry extra gas.]