Their own lawyers would be on their case if they were infringing halfway through the pipeline. They don't have to, and it would weaken their case where it counts.
> a court could find it substantially similar to the Matrix and thus copyright infringing
Substantially similar is not the standard, otherwise they would have had to stop making time travel movies about 70 years ago.
https://crsreports.congress.gov/product/pdf/LSB/LSB10922
> Under U.S. case law, copyright owners may be able to show that such outputs infringe their copyrights if the AI program both (1) had access to their works and (2) created “substantially similar” outputs
From Shaw v Lindheim.
> Their own lawyers would be on their case if they were infringing halfway through the pipeline.
This is why many of these AI companies are their own entities with sponsorships or shares held by other, larger companies. If they're on the hook for obscene copyright infringement, they just close down.
This quote is about AI, not movies. If you read the entire report, there are many other caveats and provisions:
Whether or not copying constitutes fair use depends on four statutory factors under 17 U.S.C. § 107:
1. the purpose and character of the use, including whether such use is of a commercial nature or is for nonprofit educational purposes;
2. the nature of the copyrighted work;
3. the amount and substantiality of the portion used in relation to the copyrighted work as a whole; and
4. the effect of the use upon the potential market for or value of the copyrighted work.
The substantial similarity test is difficult to define and varies across U.S. courts.