Where did you get confirmation that this is the "official" screwdriver?
Here : http://www.macbidouille.com/news/2010/12/07/le-kit-officiel-de-demontage-du-macbook-air-2010-dans-le-detail
Got a reply from iFixit. They can't replicate the official one, it's illegal...
They said mine was maybe too small, replacement driver is on its way.