is one piece episode 78 filler?

After killing the Island Eater with Hakoku, the weapons of the two giants break and they try to remember why they were dueling for about 100 years ago until their signal for battle activates. It is revealed they were captains of a crew of giants who battled anyone who opposed them.

After they each killed a sea king, a little girl asked which one was bigger. This caused the two to head to Little Garden and compare sizes, and they remained on the island and dueled to decide which was bigger ever since.