For older animation artwork, that would be true, 
since the lines were hand-inked, and restoration 
is just replacing what was there.  But for anime 
cels, where the lines are both xeroxed and under 
the paint, you CAN'T actually "restore" it, you 
are altering it.  That is why I would go for a 
correction layer, because that is a real 
restoration, and not alteration.