Nothing is being exaggerated by Goudie. The memo says Jimmy I was informing plain as day from between March 1965 to May 1969 and again between May 1971 and March 1974.

Now you're rationalizing it by saying maybe it was this or maybe it was that. Doesn't matter what it was he was a informant for nearly 10 years and its very possible he could've continued informing after this memo was distributed.

Your friend just isn't ready to example it