The issue with the plywood, assuming it is on the outermost layer of framing, is that it is now 12" away from the load bearing structure (the frame), so you have a lever arm without a solid connection between the two frames.
It may not matter in some cases - but whenever I've been involved with alternative systems like this (just a few times) the engineers always want to either see the frame designed for lateral / shear loading - or the wall system set up to take those loads.
Yes, the drywall is technically doing something, but I've never seen it included in any sort of calculation.
