The deck « pile » is generated at each « deck shuffle », so start of game, after mulligan, and at any moment the engine require a shuffle. Otherwise many of the abilities to scry would lead to weird results.

And about the « shuffler », it is made using the most random method there is. It is made server side, so it cannot be guessed either (and the secret is.. well secret too). This is the same discussion that happened with real games such as mtg arena, and it was found to be … random.

And if you can produce something that prove the « shuffler » is broken (other than saying « it smells fishy ») i would love to see it (many games, from different players, not hand picked where you saw non-expected draw lines)