The immunity was tied to any charges related to the recitation of facts in the plea and then diversion agreement. I haven't found those to see if they contain facts relevant to any violations of the act covering foreign agents.
If you read the transcript of the proceedings, though, the prosecutors clearly didn't think they were creating immunity for those. The judge did a good job of sussing out this confusion between the prosecution and defense, and that they structured the deal so as to avoid judicial scrutiny of the whole deal.
Which raises the question: why did the prosecution do that?