Yes that is what I thought ie if you didnt want to wear formal ie DJ you would need to use Lido faciiities etc. But the below is copied from my voyage personaliser packing tips - that is why i am confused:
Formal suits
Formal suits are only required on board a Transatlantic cruise on Gala Evenings and, even then, there’s no pressure to dress-up if you don’t want to. Most of our guests, however, relish the opportunity to put on a Tuxedo for one night and channel their James Bond alter-ego.