The CD is only called a "soundtrack" by this article and some retailers. The actual CD doesn't make a claim that it is a soundtrack - just that it is songs inspired by the movie.
I've often seen CD's marketed as a soundtrack for a movie. Case in point:
This cd is listed as a soundtrack
http://www.amazon.com/exec/obidos/tg/detail/-/B00005K9KF/ref=pd_bbs_null_3/104-8262482-2240755?v=glance&s=music
even thought the only song on it from the movie is song that plays durring the credits.
The soundtrack is really this cd
http://www.amazon.com/exec/obidos/tg/detail/-/B00005LNIY/ref=pd_sim_music_1/104-8262482-2240755?v=glance&s=music
Your local music store probably only had the first one in stock.