I thought that distribution of copyrighted materials was legally encumbered, not reception thereof.

Did they use a torrent? If they used a torrent isn't it likely they distributed it while downloading it?

Downloading is making a copy and covered by copyright law. Its also covered by statutory damages clause of up to $150k per violation if willful. I assume Anthropic knew they were using pirated books.

Do you have a source for that? My understanding was that both were illegal, although of course media companies have an interest in making people believe that even if it isn't true.