I think that's more likely the case actually.

When the principal company has announced an official availability date, they'll be shipping the products out to their retailers sometime before the date to make sure they'll all be stocked by the d-day. Unless they've implemented an iron-clad rule\agreement that the retailers have to follow (like Apple, Nintendo, etc) then the retailers will have the products days before the launch date to distribute.

Nokia itself will probably stick to the official schedule..