I think I get the joke. I belong to a church who is against dancing because it might lead to pre-marital sex. In fact, my mother is still concerned about the effect of English country dancing on my Christian witness. [You can imagine her concern for her teen-aged grand-daughters]
As for ballrooms on ships in Titanic's time: didn't the dining lounges have space for dancing, like nightclubs did later in the century? The band played rag-time as well as waltzes, and bunny-hugs, fox-trots, et al didn't take up a lot of space. Couples did the steps moving in a circle, but the circle did not have to be large. And the circumference of ladies' hems: there doesn't seem to be a lot of freedom of movement below the knee for making those sweeping Viennese waltz moves. IMHO it would be more the "Lawrence Welk" style of waltz, perhaps.
Maybe most of the passengers were more concerned about business conversation or smoking or strolling upon desk or a deck of cards in the evenings. Or digesting their food.
A letter or two from the period, talking about dancing on board, if any, would be helpful.