This deathrattle doesn't work as it should

Anub’arak deathrattle reads “Return this to your hand and summon a 4/4 Nerubian.”
This works fine when your Anub’arak dies. It goes back into your hand. In fact, if you trigger his deathrattle he actually leaves the battlefield and returns to your hand.

But if you COPY just the deathrattle with another card (for example, Necrium Apothecary), it doesn’t do as it says. Instead, when the deathrattle triggers, a copy of Anub’arak appears out of nowhere and is added to your hand. This is clearly not what is written on the deathrattle effect.

Please fix this so that I can play Anub’arak with Counterfeit Blade, or adjust the card text so that I can disenchant this stinker of a legendary.