They acknowledge the issue is before courts:
> These issues are the subject of intense debate. Dozens of lawsuits are pending in the United States, focusing on the application of copyright’s fair use doctrine. Legislators around the world have proposed or enacted laws regarding the use of copyrighted works in AI training, whether to remove barriers or impose restrictions
Why did they write the finding: I assume it's because it's their responsibility:
> Pursuant to the Register of Copyrights’ statutory responsibility to “[c]onduct studies” and “[a]dvise Congress on national and international issues relating to copyright,”...
All excerpts are from https://www.copyright.gov/ai/Copyright-and-Artificial-Intell...
Sure the courts may find its out of their jurisdiction, but they should act as they see fit and let the courts settle that later.
Why could a copyright office not advise the congress/senate to enact a law that forbids copyrighted material to be used in AI training? This is literally the politicians' job.