“Say when,” says the person pouring, and hands you the one job that cannot be done on time. By the moment you have seen the glass is right, decided so, and got the word out, the pour has gone on, so everyone who says when says it a little after when. Good pourers know this and slow down near the top, which means they were never really waiting for the word. They were watching your face for the breath before it. Both of you agree to pretend the guest is in charge, and the bottle quietly is.