There's a slight wrinkle to the stats, in that when you start a game, you mulligan for low cost cards. So, when the time comes to play a joust card, especially a 5+ mana card, more of the low cost cards will have been removed from the deck.
It might also make joust a little more beneficial for players with the coin (they draw an extra card, so the mulligan has a slightly bigger effect).
That said, the effect is probably very minor.
