It means that the sets were always meant to be played together, in which case Magic: The Gatherings old block format of drafts, where you'd take two from one set and one from the other, would have been more logical
Bolt the Bird (referring to Lightning Bolt and Birds of Paradise) means kill the mana dork
The real legacy of the deck is in Yuriko, the Tigers Shadow
Zac's Prize-Winning Jug Band may be a fun playtest name, but it's likely to be more of a distraction than its worth, at least by the time a set gets to development
Sure, Wizards has halfheartedly tried to answer this problem by saying the cards will eventually have Magic versions reprinted in "The List" in Set Boosters, but the list is so big and the odds of opening any specific card are so small that unless Wizards is going to massively increase the drop rate of Secret Lair reprints, it will likely end up being a wholly unsatisfactory response to potential supply issues
This size doesnt apply to inner sleeves, of course