I'd disagree, simply because you could take that to the extreme. Does he own the water he drinks, the air he breathes, the life he lives through? As far as I can see, we're talking strictly in physical items.
His definition of "I count my things as resellable items I would be pissed if someone took." would appear to cover email addresses and blog accounts etc. Maybe not much resale value, but anyone would be 'pissed' if their email account was taken.
We can take that further. If clumps of data that make up a "file" is a possession, what about the thousands of executable and library files that make up his operating system? He may not use the calculator or chess game, but his computer surely comes with that. What about every bit that make those up?
We need a clear line or this gets silly, and I think physical possessions is a clear enough line.