Hmm, TF doesn't actually distinguish between uploading routes and tracks for the newer (USB mass storage) Garmin units. This should at least change to disable the option, or we can probably support it as well.
So, yes, right now it will only upload as a track to the Dakota.
Personally I don't recommend using routes since they are limited in the number of points they can be (and thus detail), but that's just an aside.