Extended coverage insurance is added to a standard property/fire insurance policy to extend the perils of loss that will be covered. In current insurance policy forms, the extended coverage perils are already included so there is no real need to additionally specify extended coverage.
Perils of Loss
Property/fire policies provide coverage only for losses arising out of covered perils of loss. Traditionally, the standard policy only responded to the peril of fire, hence why property policies were known as fire policies.
An endorsement is a document added to the basic policy form that extends, excludes or modifies the coverage built into the standard form.
The extended coverage endorsement added the following perils to the standard property policy form: windstorm, hail, explosion (except of steam boilers), riot, civil commotion, aircraft, vehicles and smoke.
Most contemporary property policy forms already contain the perils from the extended coverage endorsement. In fact, the most basic of standard forms incorporates the extended coverage perils.
Insurance requirements in many contracts and legal documents use outdated wording and incorporate obsolete insurance requirements. As the basic property form already incorporates the perils in the prior extended coverage endorsement, it is a bit of an anachronism to still require property insurance with an extended coverage endorsement.