Did the compendium determine when the Masamune became Demonic? If not, then it's possible that there is a relation to the Masamune only turning Demonic after the dimension split? Maybe in the ideal timeline, the Masamune is no longer Demonic?
Perhaps the Masamune 'properties' are affected by the alignment of the most powerful force on the face of the planet? It was only a dagger when Zeal ruled, the alignment of that kingdom was not evil, only that of it's queen was evil and the people were just daydreaming their lives away. The Masamune had a majestic look during the reign of Guardia. Finally, it took a Demonic turn once Guardia had fallen and Porre is proclaimed the most powerful nation and they very well seem bent on conquest of the Zenan continent, El Nido and very well the entire world.
I'll admit that my second paragraph is like way out there.. But that Dreamstone is pretty tricky stuff.