Just a theory.
The Boy v Girl tribes split was a bit repetitive, but perhaps is was just Part One of a more original re-arrangement?
So much has been made about the Age divide in this series, so...
First an Individual Immunity and Eviction, to make the numbers even, and then...
Young Bucks vs Old Fogeys.
Of course the plan for this has been mucked up a bit by so much Young Blood already spilt of both genders. But it would place people in with people they would naturally ally with, hopefully preventing the feeling that "We might be technically a new tribe, but my Loyalties still lie with my old group".
Anyway.... we'll know in a few days.