What do you mean, I think I kinda get it but not completely. If I am understanding it right, and I am probably not, than the answer would be neither and both.
Actually, what DO you mean? It's a battery, it's one piece, if it rotates at one end, the other end rotates...
When you twist the unit for on/off, the battery either rotates relative to the head or the battery housing. My impression is that the foam ring grabs the battery, which then rotates against the negative contacts of the "power pack".
I've noticed that my 2AA tube the rotation happens between the cells--the top one is gripped by the head and the bottom is gripped by the nipple on the bottom. So, both?