The cart email sent from the staff client doesn't include a link back to the record in the staff client like the OPAC does. This is a problem and makes the staff cart email hard to use for tasks within the library.
I think the most common use case will probably be to send the cart/list to patrons, so a link to the OPAC makes sense independent from where you sent the mail from initially. I'll close this WONTFIX (I had filed it originally)