Nobody would know that they got an FBI tracker and that they needed to reinstall Tor to be rid of it.
Don't you think that's the point? They do this to catch criminals. I can guarentee that if you haven't looked at anything that's illegal in every way possible you have absolutely nothing to worry about. And now that we know about it, people can reinstall tor. Now it's their own fault if they get tracked.
If they were not given permission to do this, they wouldn't have.