They are just making it up. It's just nonsense.

These copyright claims are governed by the DMCA in the US. Platforms like Youtube that allow User Generated Content have a safe harbor provision. They are usually not liable for content that users post. Without that, the internet as we know it would be hard to imagine. But when someone reports a copyright violation, the platform must take it down, or else becomes liable. Then it could be sued for damages, as if the platform had pirated the content.

Posters can submit a DMCA counter-notice. At that point, the copyright owner must either sue the poster, or the content goes back up (within 14 days). It is quite suspicious, that there is no mention of that in the OP.

However, copyright owners have sued Youtube, alleging that they did not do enough to take down pirated content. This did not go so well for Youtube. Eventually they were forced to create "Content ID". Owners register and upload their content. Youtube continuously scans for that content in videos posted by users. What happens when there is a match depends on the assumed owner. They can choose to have it taken down, or to get the ad money, for example. SNAFUs are pretty common, especially with classical music. It also has no regard for Fair Use, but content owners hate that anyway.

I do not know how hard it is to get access to this. That is a good question to ask - but also read the fine print if you get access as it may not be any better than the legal process for you.