In my most recent game, I cast Etali, Primal Conqueror with no cards in my library. The ETB reads "Exile cards from the top..." which is not the same as drawing from my understanding of the rules. I end up losing the game as the game goes to show me my opponent's available spell to cast. I believe this is an error in MTGA because I should have been able to cast my opponent's spell and fail to find a spell from my own deck.