I suppose I didn't consider he was strictly speaking about Ahri's match-ups. He made it sound like a blanket statement. But when he explained, he told the player to move such that the minions would be in between Ahri and Syndra. That plays right into her though, doesn't it?
And like you said, he had Ahri move such that her back was to the river. I really don't understand the reasoning. I dunno, vs. champions with long rage poke that isn't reduced per target hit I tend to separate position myself to force the opposing player to choose between harass and spells to farm. They'll generally choose farm which opens up my own harass.
Oh, and I don't like the way he laughs at the people he's teaching, which he does quite a bit in his videos. The Ahri player took it in stride, but you can tell others were bothered. If he was just viewing random videos that's one thing, but the players he's coaching are paying him. Awfully unprofessional, but about par for "pro" gamers.