Wenger is most of the time, as we all know, very vague when it comes to details about players and signings. He was VERY clear though that Walcott had made no demands to play through the middle, and if he had that he would have immediately said no.
I believe Wenger here, and the way we have played in the last couple of games Walcott for all intents and purposes plays as a second striker. We just need a better first striker than Giroud...