Fiberglass (depending on which class of fiberglass is used) has a moderate action also, its softer and will flex easy which helps keep fish pinned IMO, it also is pretty sensitive, glass rods have improved a lot
compared to 10 years ago.
The bend of the rod is butter smooth and I don't believe you can get that with graphite.
Its also super tough, you can see how it bends in this video...