I think this is a throwback to Harald attacking ships, but no one knowing it was him.
Loki's Fruit clearly manipulates weather and creates snowstorms.
So, here's how I view it
1: Loki understands the power of this fruit, and learn from rocks how important it is, so he's been hiding it, so the world government didn't know his full power
2: Loki used snowstorms to attack people when he was a dragon, so the attacks were attributed to Sea Beasts
3: Loki with Ragnir outside of his Dragon form was able to kill Harald. Loki most likely rarely needed to use his fruit even in the new world. He's just that strong.
This makes sense if Loki was trying to hide his fruit from the world government