I think your comments are on point.
And it is true they will need to play better against ND but they also needed to play better against Auburn than they did against Arkansas and they played way better against Texas A&M.
My point is that every game has it own dynamics and it is not as though the standard of play from one game necessarily crosses over to another. Heck, the with LVs this season, the level of play in the first does not necessarily cross over the second (and given their slow start tendencies, that is a very good thing).
The LVs have been playing good defense but I think there intensity has slipped a bit and they will need to find that extra fire for ND but against a top-flight opponent, I expect they will (My optimism, realistic or not, is boundless).