It happened at the same time last year but not the year before? I do think things have changed from last time, at least for some. Children of people who were here before but left didn't arrive again, or ages were different, that sort of thing. It likely comes down to infinite universes, so there's always a set future, but there's another set future, and another. Perhaps it pulls from a random deck.
No, they talk about as if it's just Vallo being Vallo. I didn't get numbers but it's upwards of twenty. Unsure, though the timing suggests they're likely related.