Plus, someone noted that the schedule for shooting had the actors for Hook, Emma and Regina working in that VCF video, so it seems a good clue those split that way. Besides what I said was a non ship reason to split into two teams–the Charmings do not trust the baddies. Three pairs of two might cover more ground but also be weaker, as one pair might lack something. They probably will want someone with NL knowledge, someone with magic, someone who can physically fight in all teams. Then, someone the good characters trust. That is interesting set up regardless of ships.
“If I had a world of my own, everything would be nonsense. Nothing would be what it is, because everything would be what it isn't. And contrary wise, what is, it wouldn't be. And what it wouldn't be, it would. You see?” -- Lewis Carroll, Alice's Adventures in Wonderland & Through the Looking-Glass