While the points you raise are very valid points.
We feel that when a burning application is installed onto a system, and various system files are replaced during this installation. We feel its worth while checking on the burn quality to insure nothing has been broken by installing the application.
Perhaps in future reviews where a disc quality scan is included we can add a note saying "Disc Quality is largely dependent on the quality of your media and burner" this should avoid any confusion.
RE filling a media.
While this is something we would prefer to do, this is not always possible for various reasons. We can only use what material is available to us and within a timescale we can manage. But again, this is a valid point to make.