I think Berger started that rumor to cover the fact he was inserting the leftovers in Christmas rack packs
I do not think that hobby legend has ever been fully substantiated, but think Berger did encourage it. I think it is just as logical that not nearly as many high number sheets were produced in the later portions of that summer. Good thing the Mantle was a DP
The high numbers are easier to find and cheaper than the gray back "Canadians" at this point