. . . but if they already had the info, they can use it, but they will have to show that they already had it.
To prevent this from being a problem they likely question him on a narrow topic that has nothing to do with his own criminal liability.
It is bad for Trump because obviously, they are forcing him to say something he doesn't want to say.
It is good for the DOJ because they get the info they want.
It is unlikely to be good for Meadows.