This whole thread is most interesting.
There was a disucssion of upgrades to a premium cabin a while back that said AA would NOT upgrade a pax even if a seat flew empty .. IF there was not a meal loaded for every passenger in the cabin.
So that said, this 'common practice' at NRT must indicate that for some reason AA is filling J and P galley with a meal for every seat. Guess catering in NRT must be more responsive (hello .. catering . I need 3 more P meals on AAnnn) than in the US. OR perhaps AA just gives up and caters the cabins full.
Would be interesting .. typically empty seat means no meal loaded so they cannot upgrade someone.