Alan, when you read 300.22(C)(2) Exception it tells us that "This section (meaning Section 300.22(C)) does not apply to the stud spaces of dwelling units.
I've had this discussion with Jeff Sargent from NFPA and that's his understanding also. Job is approvable.
For the sake of the disbelievers, I've seen contractors take a piece of metal panning material 3½ by 24" and nail it on above the box and band it around the box and nail it below the box. Now you've divorced the wiring from the air flow.
