Well, I wasnt going to say anything because I figured my answer was out in left field. But with your idea that one copy goes to the acknowledged second prosecutor I will add my thoughts.
My immediate reaction was that both President Trump and also Q wanted copies for personal posterity reasons. I now think, with the inclusion of your thoughts, that Q and the President want one copy to do their own research on. That would give us a total of the three original copies.
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By asking the way Huber did, there’s no official record of the copies, just the word of the whistleblowers.
Maybe they need the separate copies because deep staters in different prosecutors offices altered one or more submissions. Three copies, one to Huber, one to other prosecuter, one to IRS. It could also be just a simple matter of chain of custody. Each office needs a clean submission if they are going to use it as evidence in indictments.
Re Huber losing the 3 copies:
What if they wanted to compare the 3 versions forensically for discrepancies?
By asking the way Huber did, theres no official record of the copies, just the word of the whistleblowers.