Mainly it just boils down to situations where the player has little input on what happens. If random events can kill you before you get a turn, if something happens that you can't avoid unless you started dodging before there was any observable cue to know it was coming, if you can get into situations where you don't have any means of avoiding damage/defeat/etc, that is fake difficulty.
--
We clasped our hands, our hands in praise of a conquerors right to tyranny