Well I heard something really amazing about this a couple years ago you can take it for what it's worth:
When the Aid book was being revised and transformed into the Insight book, the main brother editing the job saw the 7,000 year creative day thing and traced it back to a Jewish rabbi that taught that. He called the head of writing and said that's where this 7,000 year creative day idea comes from, and I think we should drop this- it's gotta go.
And he agreed and so they did. These two brothers right then and there snipped it out and also it was taken out of the SI book (All Scriptures) around the same time, which would have been late 1980s when the Insight books came out.