It may be that Siliconera was downloading from the sole, wheezing server that Nintendo has set up for the time being. Also, Nintendo may be rolling out a greater number of servers come release day and that would serve to reduce download times. This could have just happened to be a particularly slow test. However, it doesn't look like Siliconera repeated the test.
Remember that there are two factors involved here - the client-side connection, and the server-side connection (and everything in between, but generally that's not too slow.) The problem could have either been at Nintendo's end or Siliconera's end.
