What behavior are we talking about here? knife cookbook upload?
Right now, knife cookbook upload reads metadata.rb and ignores metadata.json. It generates the data from the .rb file, and uploads that. It does not create a metadata.json file, on disk or in the cookbook itself--this is just metadata in the cookbook object.
My understanding is this ticket wants knife cookbook upload to read metadata.json if it exists, only reading metadata.rb as a last resort if metadata.json does not exist. Everything after that would work the same: no files are actually put on disk or into the cookbook. Is that correct?