Well, surprise, but while digging around doing etymological research (i.e., digging in Ralph Allison's published papers), I might've found a source of the urban legend: Allison's "Critical Issues: MPD & DID Should Be Used For Two Separate Groups of Dissociators" CANDID (California News of Dissociation and Identity Disorder), 3(3):4, 1995. (And apparently I even knew about this back in 2011 when I first blogged about this stupid urban legend, but I didn't dig deeper or put two and two together.) This paper is worth discussing, just because... well, it's crackpot as hell, and a nice example of why you shouldn't believe everything a therapist tells you, no matter how famous or (once) well-respected they are (or were).
( This started as us reading a stupid paper about this guy's cracked ideas, only for us to get sucked into pointing at it as a stellar example of why therapists should not be treated like gods. )