I tend to give S10, incomplete pass, at least twice, no matter how obvious the call is.
1: If I ever give just one wave, it doesn't feel right. It feels like I'm giving a lazy lackadaisical signal.
2: Even if the incompletion is obvious, maybe the contact wasn't. Waving twice sells a PI no-call better. I fear waving once suggests hesitancy.
3: Other waving signals are repeated as well - timeout, touchback, winding - even when obvious.
Am I way off base here? Is a second S10 wave really frowned upon in higher circles? If so, I guess I can cut it out.