It uploads your PDFs to Elsevier servers for storage. By design. Asking how that could lead to Elsevier obtaining evidence of paper piracy is like asking how u

It uploads your PDFs to Elsevier servers for storage. By design. Asking how that could lead to Elsevier obtaining evidence of paper piracy is like asking how using gmail could lead to google using your email to do targeted advertising. You are giving them everything they need to do it, so of course they might do it! The position that needs defending is the supposition that they can't.