I am a reseller for Canto, and also the one who works with and for alash, and I want to explain this as well as I can. Canto is able to import all of the metadata added by Adobe products because it always writes the metadata to the top part of the header of the code within the asset in the same place. Canto developers complain that they are unable to import all of your metadata because it does not match the same criteria, and they don't wish to search through the entire file. If your data was consistently written to the top, in the same manner, then it would be found and imported. This is the explanation which was given to me when I was trying top track down the problem from Canto.