They have no reason not to do this
Easy mode - XY ORAS level difficulty
Normal mode - Same difficulty as the old games
Hard mode - BW2 challenge mode USUM level difficulty
Lunatic mode - Drayano level difficulty

Hard and Lunatic mode would have less tutorials
Hard mode has a level cap set at the gym leaders highest Pokémon
Lunatic mode has a level cap set at the gym leaders lowest Pokémon
You can change between the 4 difficulties at anytime in the settings, you can also turn enable or disable the level cap in the settings