I think that it’s necessary to clarify some aspects of this fields to avoid destructive edits.
For example in https://musicbrainz.org/edit/56215749 the editor most likely thought that, as this is a digital release, it does not have a physical barcode. It would be helpful to rename the field as “barcode / digital UPC” or something similar as to avoid this kind of edits.
Also, automatically transform “https://itunes.apple.com/album/*” to “https://itunes.apple.com/us/album/*” would help to avoid the idea that a release with the former syntax is a worldwide one (when in reality both of them are identical) (view the related edit https://musicbrainz.org/edit/56215750). Maybe with a message to clarify that this is the case.