I can't say I've ever seen a cel with one of 
those "trace layers" (I actually prefer to call 
them "line enhancement layers", since that seems 
to be the purpose) which does not *also* have 
lines on the cel layer with the paint as well. 
Obviously, I haven't seen this particular cel up 
close. . . But I have at least five other 
examples of cels with line-only layers, and none 
are missing the lines on the layer with the paint.

One thing that is possible is that someone at 
some point took a pen to the cel to make it look 
better. Seems people who do this rarely retrace 
all the lines, only certain ones - like tips of 
hair, eyes, and edges of features like chins and 
jawlines. . . This is common and would logically 
explain the strangely sharp and dark areas of 
lines which otherwise aren't there.

Many Sharp Smiles,
--Drac