Why does the game automatically start a NG+ after endings...

so after finishing Dark Souls 3 (my first souls game) and liking it a lot, i've picked up bloodborn: GOTY edition. So now i defeated the last boss and wanted to play the DLC... but the game automatically starts a NG+ for you after finishing the boss? What the? As a player i expect to play the DLC AFTER the last boss, isn't that the proper order? I mean the DLC is released some time after the vanilla game, so players must have killed the boss at that point.

And the worst part is, if i want to wittness the DLC in its normal difficulty i actually have to start a new character instead of the NG+ one..