when king enters speed mode his sword wasn't coated by the flame, so the condition still stands.
flames on = durability
flames off = speed
Not sure you understand what i said so I will say it again
the flames specifically on the back of his head does have a relationship to how durable king is but
1) that was made with respect to his body not his sword
to illustrate my point , when king's sword has no flames on it, I dont think it is faster . thats never established in the story.
didnt really see much to write home about in his armament haki
so calling it the first (wrong) or second(also wrong) hardest blade in the world is rubbish and based off a faulty premise.
dont even know its grade
laughable