To me, a seamless chamois is a chamois that is all one piece, so the only stitches are the ones around the edges to attach it to the shorts. I think most are like this now. Years ago I had some PI shorts with a chamois that was multiple sections sewn together, and then sewn to the shorts around the edges. So you ended up with seams between you and the saddle, sometimes in high-chafe areas -- very uncomfortable.