Bill,
Everything you quoted pertains only to 85-fold packs. Yes, I mean that when viewed in landscape mode, the bottom flap (containing text) should overlay the top flap (containing the pate anyplace kid or the ad graphics). Upon examination in person, I can tell whether the pack is real or not without regard to this property. EVERY SINGLE real 85-fold pack I have ever examined (including all of Ernie's stock, several personal collections, full boxes, etc.) has this property. EVERY SINGLE 85-fold pack I've examined with the flaps reversed has been verifiable as fake without just relying on this property. To me that is conclusive.
When it comes to 21-fold packs, the upper flap almost always overlays the lower flap. The only exception I have ever seen are the 5th series yellow 21-fold packs you are referring to. I have owned or examined two of these with the lower flap on top which were definitely real, as yours probably is. They are obviously all from the same box (I got mine years ago from Dan McKee) and that is an exception to the almost universal rule for 21-fold packs.
I should ad that wacky ad packs and poster packs (whose fronts are horizontally oriented) seem a little odd when you first examine them because the ad is upside down compared to the front of the pack. This is the way they should be, with the upper flap overlaying the lower (like a 21-fold).
Let me know if anything is unclear. The seller of the pack in question claims it did not originate with Tedjeffrey, and that may be true, but it is still fake.