Ron -- i'm absolutely no authority on the history of the various Randall sheaths, but I'd like to comment from the perspective of a guy who's assemebled a fair number of heavy duty leather sheaths.
I blew up your 2 closeup pictures as far as I could until I started to lose resolution, and to me it looks like Moore and Heiser used two entirely different stitching patterns. Moore's zig-zags don't appear to be saddlestitched, but rather a single running stitch. That would seem contrary to common wisdom about stitch patterns and durability, saddle stitching being by far the preference of makers who want real long term wear in their work.
And I can't see any noticeable difference in the spacing either, so if I were to try to give a reason for Moore's reputation for long lasting leather, I'd look to something like the quality of the leather he used, or perhaps he had a "secret preservative". The stitching can't tell the whole story, methinks
Having said all that - definitely some classic pieces, thanks for the views
Mike