I understand what you are saying, Mark, and once a photograph is bought, it is out of the artist's control on how (and where) it is displayed. But for some of us, the color and size of the mat board was chosen by us to complete the work -- not just as a framing devise to be discarded/changed. We might be as disturbed by someone changing the mat color as we would be if someone changed the size of the window opening and significantly cropped the image. As far as the conservator is concerned, the "original" print was not altered or changed, but as far as I am concerned, it is not much different than someone spray-painting a bronze sculpture so that it would match their couch.
This is a personal POV. Many folks sell unmounted prints and let the customer do what they want with it -- and that's cool with me. And if I sold prints made by a machine or printed by someone else, I probably would not care as much about how the final piece (matted and framed) looked like.
My carbon prints and platinum prints are hinge-mounted behind the window -- and are signed on the mat and on the back of the print. My silver gelatin prints are trimmed to the image and dry-mounted behind a window about a half inch bigger all around than the image -- signature directly below the image on the board the print is mounted on.