Seller bought them off a buddy and re-sold them. His buddy used them for Chia (XCH) mining. The buddy knew what he had, likely didn’t care about taking a loss offloading them to seller, seller didn’t know what he was holding onto.
This corroborated by the seller telling me (my buddy used those for bitcoin or some shit, idk), and all of the drives still having Chia plots on them since he didn’t bother to reformat them.