It seems logical to assume that the shard worlds only experience the Calamity that destroys them, but logic only gets you so far. There's no confirmation. It's on the "if it's not answered in Shadowbringers, we should probably ask the devs" list, lol. I suspect that the Ascians are weakening both sides of a single shard/Source barrier at the same time, meddling in both dimensions to create enough instability to finally blow out the membrane and rejoin the shard world.

As far as a lore wiki goes, curation and moderation is indeed the challenge. It takes so much time to do data entry, one loses time for actually acquiring and archiving data. For what it's worth, Gamer Escape welcomes any efforts to flesh out the lore and (through their Discord server) will do their best to accommodate any changes needed to the infrastructure to make lore work easier.