I am not sure why you would think so. AFAIK we will see more what courts think later in 2025 but judging from what was ruled in Delaware in feb... it is actually very likely that LLMs use of material is not "fair use" because besides "how transformed" work is one important part of "fair use" is that the output does not compete with the initial work. LLMs not only compete... they are specifically sold as replacement of the work they have been trained on.

This is why all the lobby now pushes the govs to not allow any regulation of AI even if courts disagree.

IMHO what will happen anyway is that at some point the companies will "solve" the licensing by training models purely on older synthetic LLM output that will be "public research" (which of course will have the "human" weights but they will claim it doesnt matter).

I'm interpreting what you described as a derivative work to be something like:

"Create a video of a girl running through a field in the style of Studio Ghibli."

There, someone has specifically prompted the AI to create something visually similar to X.

But would you still consider it a derivative work if you replaced the words "Studio Ghibli" with a few sentences describing their style that ultimately produces the same output?