Sure, a license can't create new legal understanding of "derived work", but I think the intent of what Splinelinus said still works: a license outlines the terms under which a licensee can use the licensed Work. The license can say "if you train a model on the Work, then here are the terms that apply to model or what the model generates". If you accept the license, those terms apply, even if the phrase "derived work" never came up. I hope there are more licenses that include terms explicitly dealing with models trained on the Work.
Also, for comparison, both GPL and LGPL, when applied to software libraries (in the C sense of the word), assert that creating an application by linking with the library creates a derived work (derived from the library), and then they both give the terms that govern that "derived work" (which are reciprocal for GPL but not for LGPL). IANAL but I believe those terms are enforceable, even if the thing made by linking with the library does not meet a legal threshold for being a derived work.
