This rule, as far as I know, harkens back to the good old days when GMRS was in its infancy; Basically prohibiting the use of Autopatches which were prevalent on many 2m Ham Repeaters. Used them myself on occasion back in the day - cue "I've been a Ham for 30 years" speech. The now ubiquitous cell phone pretty much killed them off, although there are a couple in my area still out there...