The replacement effect from Suplex's first mode will exile the target creature if it would die this turn for any reason, not just due to lethal damage
The lower minimum compensates for the lack of consistency in the format when building decks, allowing players to consistently play the cards they plan around without waiting forever to draw their one copy
That setup gives you the full multiplayer experience, complete with shifting alliances, table politics, and several opponents who may or may not remember that you attacked them six turns ago
Those wont be as relevant to us, but as well discuss, if a foil hits it big (Expressive Iteration, Im looking at you!) suddenly thats a very relevant number
This is useful for Arceus EX, as it lets you get more cards in your Bench so its attack is stronger