From the linked Ars article:

> Notably, the flagged downloads spanned seven years, starting in 2018. That’s about four years before Meta’s AI efforts “researching Multimodal Models and Generative Video” began

> Instead, Meta argued, available evidence “is plainly indicative” that the flagged adult content was torrented for “private personal use”—since the small amount linked to Meta IP addresses and employees represented only “a few dozen titles per year intermittently obtained one file at a time.”

Personal use sounds plausible to me when imagining something like 70k employees and a bit of a "bro" culture.