Only practicality it offers is knowing what your opponents move is for a switch. So they use something that can hit Shedinja, you can almost guarantee that they will use that move again the next turn, allowing a safe switch into another member on your team that resists that move. Shedinja is still slow as shit though. Even with the sash it will still most likely only get one attack in. He doesn't exactly shine offensively either. With the right set up, baton passing a speed buff, etc. the strategy may sound great but it's too situational to be effective and reliable.