You'r going by few lines of text by some unnamed Sony rep, who is not even talking about their financial reporting... It does not say anywhere in your link that they use sell through as the number in their financial reports.
Sony can't have up to date information on exact sold to consumer numbers, when the retail channel is so huge, but they do have the information on how many they have sold to retail, and there is absolutely no reason why they shouldn't use that number in their reporting.
I quess I have to try to google some link for you, even if it's common sense...
edit: You have to understand that when Sony has sold an unit to retail, it counts as a sale for them, whether they got paid on it already or whether it's sales receivables in their balance sheet. They are not going to report lower numbers, just because a retailer hasn't reselled their inventory yet.