Not really? Nintendo sets the date for their releases, but breaking street date happens all the time. And not just with video games either. I work in a bookstore and a video game store, and we receive lists of release dates (for both jobs, so I would assume Best Buy would have access to those as well). Plus, it says right on the boxes, and plastered all over the packaging, DO NOT RELEASE UNTIL XX DATE. And this has happened to me several times at Best Buy, when everyone and their mother broke street date for Fire Emblem, and they wouldn't give me a copy. And yet, they had Pokemon Conquest on their shelves, but when I took it up to the cash, sorry, no can do?
The thing is, the most Best Buy will take is a regulatory fine for breaking street date, since it's not as if Nintendo is going to stop shipping games to big retailers. If it was a small independent store, that would be a different matter. Imagine an independent store trying to get by without being able to sell Nintendo product because they violated street date and they have refused to allow them to sell any of their future games.
It's Nintendo's date, but the stores have to uphold it. If they ****ed up somewhere, that's not the customer's fault.
Also, I don't shop at Best Buy anymore, but that's a moot point, I suppose.