this interesting, but unfortunately, not dated, so I don't know if this information is still accurate. It seems to say that insurance companies are required to provide sinkhole coverage , although as a rider, with extra premiums. Of course, if it is accurate, they can effectively get out of it just by charging more than anyone would want to pay.
https://www.myfloridacfo.com/divisio...lapseGuide.pdf

Incorrect
 

Catastrophic ground collapse is included in property policies in Florida. Coverage has specific requirements for coverage. First, ground collapse must be sudden and damage to structure. This means if sinkhole opens up in yard, next door, across street and no immediate damage to structure there is no coverage.

Sinkhole coverage does not have those restrictions. Sudden and immediate damage not in coverage wording.

At one time sinkhole was included in all policies but the state changed the coverage to catastrophic ground collapse with restrictions and made sinkhole an optional coverage by endorsement. Companies had option of filing 10% deductible or all perils deductible.

Allstate and State Farm elected all perils deductible. That means if you purchase a $500 deductible and you qualify for sinkhole endorsement the deductible will be $500. There are a few other companies that elected all perils deductible but not sure who they are. The premium will be a little higher but a whole lot less out of pocket if you have a claim.

Having a local agent who is available to answer your questions, takes the time to explain coverage and go over the actual endorsement with you gives you a better understanding of how it works.

As for denying to write a policy due to sinkhole within certain radius...Yes companies can do this. When the state first changed the policy coverage in early 2000’s most every company ran a report on sinkholes by address. Many actually charged the client to run the sinkhole report and had you sign waiver that fee was non refundable if coverage was denied.