Here's a difference in character between the inside of something like the ISS and a spin-habitat ship/station though:
On the ISS they have zero-G everywhere, so they can, very efficiently, pack stuff on the 'floor', 'walls' and 'ceiling' because you move around the station by floating in the middle of those surfaces. However on a spin habitat, the whole point is that you have a more or less conventional floor, that you have to walk on, and on which you can't put things that you don't want to tread on, and an equally conventional ceiling, where you can't put things that you don't want to fall on you. Also, the entire point of a spin hab is to provide space for conventional living, which includes walking around and exercising, so cluttering it with storage kinda defeats the object.
IIRC, Hermes' supplies arrive in resupply modules which dock to the spine of the ship, so moving bulk cargo 'downwards' from there into the spin hab is going to be a pointless PITA. Better to stow it in the zero-G spine and only take it to the spin-hab if and when you need it to be there.