Hashier - there will always be a small delta between the Echo Nest and the Spotify ID spaces due to a number of technical reasons. GoonRock (aka spotify:artist:53sIBaVjXQhfH89Vu6nEGh) is a mapping that we don't know about yet.
You can create a taste profile with all of your iDs with a single bulk update request and then read back the data.
Paul