If they're hiding it, they know it's illegal.

Meta allegedly concealed seeding

Supposedly, Meta tried to conceal the seeding by not using Facebook servers while downloading the dataset to "avoid" the "risk" of anyone "tracing back the seeder/downloader" from Facebook servers, an internal message from Meta researcher Frank Zhang said, while describing the work as in "stealth mode." Meta also allegedly modified settings "so that the smallest amount of seeding possible could occur," a Meta executive in charge of project management, Michael Clark, said in a deposition.