Kek! That is exactly what I thought when I hear about it. They should call Mueller's bluff.
It's one thing to get a grand jury picked from the DC population to indict someone after a one-side argument. It's quite another to convict them in a real trial with defense lawyers picking the case apart and JA being called as a witness.
That would be a good excuse for Trump to pardon JA, so that he can safely come to the US to testify.