Hearthpwn

Been having a lot of fun recently with a Starship Hunter deck. Did not expect the interaction between Parrot Sanctuary and Cover Artist to work as it has been when changing Cover Artist to copy a deathrattle minion. Maybe someone could help me try to understand it. This seems like a bug, although a helpful one for my games with this deck.

Current Interaction:

1. Play Parrot Sanctuary with a Deathrattle minion already in play.

2. Activate Parrot Sanctuary and play Cover Artist (whose cost is now 3) to become of a copy of the Deathrattle minion.

3. See Parrot Sanctuary become active again, indicating that a Battlecry minion has been played, but any other Battlecry minions in your hand retain a 1-mana discount, like Cover Artist was never played.

4. Activating Parrot Sanctuary again will reduce Battlecry minions' mana cost by 2.

I have only seen this occur when turning Cover Artist into a Deathrattle minion. Every other time the cost reduction works as expected. But in this instance, the cost reduction is basically applied twice. Thoughts as to why it is happening this way?

Thanks!