Could someone explain me this

So i got started on playing the story line in ASE single player and a question i have is do i have to beat all bosses on the alpha difficulty to progress the story ?

Like am i blocked from watching some cutscene or some piece of the lore if i dont beat all bosses on alpha or could i just beat the bosses on the lower gamma or beta and still get the full story and cutscenes before going to the next map ?