

That’s like asserting that a self-defense claim is an argument that you didn’t hit the other guy. You really did hit him (copyright infringement / assault), but you have a defense that admits the literal facts but absolves you of liability (fair use / self-defense.)
You don’t need to argue self-defense if you can convince the court that you didn’t actually hit the other guy.
That is only true if the pieces were originally protected by copyright, the pieces extracted were substantial enough to retain that copyright, and their use in creating a “trace” model was enough to convey that protection to the final work.
I don’t know why you keep insisting that fair use has to come into it, or that a fair-use argument is not worthwhile outside of a court. (Sure, a judge would apply the binding precedent to determine if a fair use defense applies–but that’s true of every other part of the tort as well.)
Most claims of amy sort, copyright or not, are settled long before a judge gets involved.