When the 2-Disc LE “GOUT” DVDs came out, I bought the full screen bonus disc on ebay just so the spine would match all of the others. It is exactly the same disc that was in the widescreen box set when I had it.
The bonus material on every Lucasfilm DVD release was universally the same no matter if the main presentation was widescreen or full screen. Sometimes the disc art might even say widescreen or whatever, but none of the bonus content ever differed in aspect ratio. Even the 2006 GOUT discs which were sourced from laserdisc masters and were considered “bonus material” were still in non-anamorphic letterbox even if you bought the full screen DVDs.