To me OT, that implies the deck is stored as an array, and that Rewinds simply push all the cards down the array and put the rewound card at the top. This would mean that the deck is shuffled prior to the match and is actually set during the entire game.
I don't think the deck is set. In a desync match my AI supposedly drew diff. cards than the cards I actually drew according to my opponent.
I think this should be investigated. (one occurrence could be a possible mistaken memory)
Does anyone know how to cause a desync?
Also Mindgate is evidence that the deck is likely to be set during the game. The automulligan mechanic also seems easier with a preset deck and shuffling since the deck is prepared at the same time as the hand instead of with two different functions.
It could be that the deck is arranged arbitrarily, and the deck itself is never in one specific state... all except the top card. Since Rewind obviously depends on the top card, as does Mindgate, while no other cards affecting the remainder of the deck exist... basically, I don't think the deck takes on a fixed state, save for the top card. However... multiple Rewinds seem to stifle this...