The difference I see between Manafort and Cohen is the Podestas were involved with Manafort in the Ukraine case. If the Manafort case was kicked back to district court, would the Podestas also be indicted? Is Mueller protecting them now or saving them for some larger case?
In the Manafort case, the issue is not change of venue, it is change of prosecutor.
Mueller is not going after Podesta. Podesta has no connection to Trump. Mueller's charter should be limited to Trump campaign, but he has taken it as anything (ever) dealing with people who were in the Trump campaign.