He doesn't have to be disruptive, just difficult to move. If the offense can't get him off the ball then it always has to go around him. That's why you see offenses generally start with a quick double of the NT, to try to get him started moving in a certain direction. If they can do that, then either the guard or center peels off to go get a linebacker on the second level. If they can't, then their first responsibility is to move that NT.
Now, there are schemes that rely on the NT to absolutely be disruptive. I believe Eberflus just wants him to keep the linebackers clean by holding up the OL for as long as possible. Of course, I think every DC would love to have an NT that not only can hold up to a double-team but also destroy one. They definitely want an NT that can destroy single-blocking and at least force offenses to double him.