Based on some PMs I had related to Sonic, the threads were from late '09, so the search function won't find 'em.
The Fall 1991 date does make it tougher to pin down which came first, especially if we don't know how the mini was distributed. I don't know if this was on the stands with the regular books, a video game promotion, special order, etc. I know several people on these boards look up print runs & distribution figures all the time. Maybe there would be some data for the fall of '91 months (and/or the months preceding?) that would tell us when it shipped/came out (if it was, in fact, on the stands). If not, I'm still stumped.