The current documentation is a bit lacking. I think some better description of what it does is needed. Ghostscript is supposed to be used with an InputAttributes dictionary (possibly set via setpagedevice at the beginning of the job, or other hardware mechanism if used in an embedded usage) which describes what are the available media, and what attributes they have, to know what media choices is available, and try to match that to media selection setpagedevice calls. In the absence of an InputAttributes dictionary, most media selection setpagedevice calls are dropped; this seems to be overriden by the -dMEDIAATTRS switch, which allows them to pass-through. AFAIK only two drivers do anything with the information, - pcl5 and pxl (for MediaPosition/tray selection), and may be one or two of the 3rd party drivers. See also bug 687899, trunk@5831, trunk@5995, for background information, and Resource/Init/gs_setpd.ps for the actual NOMEDIAATRS conditionals, and also some recent discussion in Bug 692914 (Postscript MediaType lost in tranformation to PCL).
Report is already 6 years old and no additional complaints. Closing.