The 7th calamity seems to be different because Bahamut was stopped before he could do too much damage and phoenix released the aether back to the world. (I do wonder how the Ascians would have stopped Bahamut from destroying the whole world otherwise...I mean they still need people and the planet to still be there to have their future..)

The ones before took some time to recover because they often destroyed the civilizations with it but I also wonder if the source would have ever gotten over that. 200 years in the future the people still thought it would be better to kill themselves by changing the future than continuing to exists. We knew already that it would turn the soil bad but seemingly it even went after other ressources and destroyed that too...so maybe this would have been another mistake by the Ascians (since they too did not know 100% what the weapon would do in combination with a rejoining) because even if some survived and rebuilt, more and more parts of the planet would be uninhabitable and thus bad for the Ascians too.

And no I think this future has shown that there would need to be more rejoinings to happen before Zodiark is free.