I think given that we see posts all the time of complaints by players that they are frustrated with x boss/creature/event in the game giving them trouble that there is some merit to saying that there can be challenges to some, at least until they understand how to overcome those challenges.

But one can also by choice make it a harder game to play as well (all sorts of challenge type runs).

I'd not get so hung up on the marketing language to be honest as its meant to be subjective.