Considering TTI did some weird stuff near the end I suppose its possible that some Duos came with a copy of Y's that had a back insert, but I can't help but wonder what the logical explanation would be for this.
The Duo version of this game has "Turbo Duo" branding on the CD. Why would they bother to make new screen art for the CD but reprint the old back instert (no TTI-era game, AFAIK, has the old NEC-era graphic design on the case). For that matter, if they were interested in back inserts, why did the GoT 3-in-1 never have one?
The only thing I can think of is that, for whatever reason, they must have run out of Y's CDs before they ran out of GoT CDs (how? since they are distributed in the exact same frequency?*) and commissioned a reprint of Y's with an American CD plant. At this point back inserts were probably included in the deal, and so they just printed them because they were free. It would help a lot to know if the version with the back insert came before, or after the one without. I'm tempted to say before, because I had my Duo somewhat early on and there was no back insert. I think it was October 1992. That one developed problems so I exchanged it at EB for a December 1992 one...I think. Someone here has my old US Duo. I think it might be Nat.
If this were the case then the manual must be printed in the USA as well? I don't have very many US games, but the ones I do have that were made in Japan have Japanese books and CDs, and the ones I have that were made in the USA have USA books and CDs.
*Did Super Systems Cards come with just the GoT 3-in-1, or did they also have Y's?