We don't know for a fact the souls in the Void were destroyed. The voidsent (which I will note are what the people of that shard became) retained their complete sapience after transformation, unlike the knock off angels we saw in ShB. The shard itself is wrecked, but research is being conducted into ways that it might be restored.

Incidentally, the Flood of Light occurring on the 1st wasn't actually a mistake. That was planned for.