The seed plants a world-building principle: the Grand Line is a machine of weather whose storms function as anti-predator throttling — even apex creatures (a WGS-tier swordsman) have their destruction interrupted by the environment. The principle recurs:
Reverse Mountain (Ch. 101-102): the Red Line’s currents force ship-paths
Skypiea: weather-as-vertical-geography
Florian Triangle: weather-as-ghost-zone
Calm Belt: weather-as-Sea-King-cradle
Punk Hazard: weather-as-arena-divider
The Grand Line’s weather is treated as a sovereign actor in the world. Predictive use: in any chapter where the Grand Line’s weather interrupts a fight or saves a character, the interruption is not coincidence — it’s the Grand Line acting on its own terms.