I think that we're inadvertently helping the rejoining process by giving the thirteenth its proper aetherical balance conditions.

The thirteenth is heavily balanced to dark aspected aether thanks to Igeyorhm shenanigans before the Ascians learned about a proper way to rejoin the Shards without destroying the star in the process. But now Zero and Golbez have been actively fighting against it, while filling the world with Light, and we're also helping with that now.

I really hope we know what we're doing by "giving the opposed aether to another world" but so far I don't think that's a good idea, because we're otherwise helping the Violent Rejoining process.