Who knows where these rumors may have begun. I remember when it was supposedly true that the original three-panel Cinerama negatives for How The West Was Won were destroyed after its original run and the after composite 35mm negative was made. This turned out to be untrue as they were stored in an underground film vault in Kansas all that time. They were pulled out and used to make the beautiful Blu-ray disc now available. In the era of the Disney O&H reruns, the shows probably would have been edited via 1" video tape transfers rather than the film itself, since it's so much easier to do.