As I said, an ordinary person has little interaction with the state, so there are fewer direct opportunities for harassment. Moreover, the state has little reason to harass the usual persons offered amnesty from prosecution, since those people have usually not been in direct opposition to the state itself – they are usually just criminals.
However, if they had been in opposition to the state itself, it would probably be a different story. For instance, I don’t think Snowden could ever fully trust a (theoretical) offer of amnesty from the U.S. government. A similar situation (to the VW one) exists with employees of the state who continue to be employed by the state – they interact with the state more (in its role as their employer), and more interaction means more possibilities of harassment. Also, even some people who quit their jobs would be affected; these would be people who were employed by state actors which have a lot of interactions with people in general, like the IRS, the DMV or the Police. I would imagine that former employees at any of these organizations who quit their jobs and turned whistleblowers would experience trouble from their former employers. On the other hand, a whistleblowing former clerk from, say, the Department of Veterans Affairs, would probably not.
What I’m saying here is that there are two factors: The degree of interaction a person has with the organization after the event, and the degree to which the person was percieved to be in direct opposition to the organization itself. The VW employees score very highly on both these factors, while the median person offered amnesty from prosecution from the state usually scores low on both.