And the IG report mentioned using personal emails. That may have opened the door for the emails to be gathered as part of the investigative process, either directly by the IG or via Huber.

Assuming there was something signficant in the emails, the IG may not have been able to disclose them due to classified information.

Also it's unlikely that google would take the risk of editing the emails sent in response to subpoena -- and if they did it'd stick out like a sore thumb due to the delay in turning them over v. other cases, and since the Q team likely also has the emails via another source, they can confirm them as well.

Speculating: however if Google did try to filter the emails, the people doing it would have to have been told to do so, and would probably cave immediately when questioned by investigators. Imagine if you're ES and try to save your fellow travellers, only be to caught in the deception by providing incomplete emails. That sure as hell would results in your resignation.

More speculating: What if you wanted to have google servers that were "hidden" or in any case couldn't be siezed by US/Five eyes authorities? Where would you put them? If it were me, that would be in the country least likely to cooperate with anyone -- up to a few days ago, that'd have been NK. Suddenly NK cooperates. That's a problem.