That's the same situation.

If the GM has been letting the players just kick in the door and kill the antagonists or die trying the entire game and then throws something more complex their way without any warning or any reason in-game for the characters to approach it differently, the GM is the one to blame if the characters continue to play in a way consistent with the previous narrative.

Don't change what kind of game your running without warning or you have no one to blame but yourself hen things go wrong.