> Genuine question: if I train my model with copyleft material, how do you prove I did?
The burden is on you to prove that you didn't.
> Genuine question: if I train my model with copyleft material, how do you prove I did?
The burden is on you to prove that you didn't.
No it is not. It is exactly how the burden of proof works.
https://en.wikipedia.org/wiki/Burden_of_proof_(law)