Gasoline will not eat or damage fibergalss. For years a number of builders, including Bertram built their boats with fiberglass tanks. Ethanol is damaging fiberglass tanks (along with fule lines and various fuel system components) in older boats.
If gasoline does not damage fiberglass, then what causes that fiberglass damage where fuel comes in contact with such surfaces - particularly with repeated contact? Air? Water?
A buddy of mine still has the hull of an old (Early 70's) that has shown signs of damage from gasoline exposure where there apparently was a minor gasoline leak from the fuel line to the engine. Just where the fuel dripped, there is an area where the fiberglass has delaminated (or whatever it is called when it gets eaten). The surrounding area is relatively intact, even where the paint was worn/damaged.
If fiberglass is coated with some special sealants - then yes, they are more gasoline-resitant. This may be what you were referring to. But fiberglass itself is damaged by gasoline. And any such coating that gets damaged then allows the gasoline to react with the fiberglass.