That's how my brother met his wife. Years ago he and his daughter were put in a shared cabin with two other people - mixed sexes!
I can't explain it. Years ago I chose shared accommodation on cruises but was put in with other women. One of the girls in our cabin was on her honeymoon and they could not afford a double cruising from Vancouver to Australia. Every afternoon the other 4 women and I would leave the cabin for a set period of time to give the couple some privacy.
I was rather shocked when my SIL told me that they met on a major cruiseline when they cruised out of Singapore. I think there were 2 men, 3 women and my young niece. I know that neither my brother or SIL knew any of the others but the adults were all teachers, so perhaps it was set up by someone outside the cruise line. "Anyone willing to share a cabin with 4 other teachers for a really cheap cruise?"
Anyway, DB and SIL are currently travelling and off the grid so I can't ask. I always thought the story was bizarre.