Presumably, Hernando County lost before the circuit court and then won before the Fifth on the basis of the McBride case - which dealt with "compactness" as a criterion for annexation (not "pockets"), but without much explanation.
Here's the entire opinion:
Petitioner is challenging two annexation ordinances on the basis that they
create an impermissible “pocket” of unincorporated area within the municipal
boundaries. Concluding that the lower court departed from the essential
requirements of the law, we grant the petition and quash the lower court’s
order. See City of Center Hill v. McBryde, 952 So. 2d 599, 603 (Fla. 5th DCA
PETITION GRANTED; ORDER QUASHED.
The Fifth keeps behaving in very unpredictable ways in these cases. Compare its treatment in the City of Cocoa case. One can only conclude that the treatment one of these cases gets in this District is totally dependant on the panel you pull rather than the facts of the case.