They crumbled after that.
But keep in mind that a Signature Win is in context to that program...Marshall beating ND in '22 was a Signature Win for them, but USC beating ND in '22 was not a Signature Win for them.
Considering our current standing in the College Football landscape, Signature Wins for us would definitely be like Georgia, Bama, Tosu, Oregon, maybe FSU if they come to South Bend undefeated, maybe Clemson if they rebound to show they are elite again.
We are in that Very Good but not Elite range...beating a team that propels us to being considered among the Elite would be a Signature Win for us.