Yeah, that's the hypothetical that should definitely be played up – "buying" a movie and Apple terminating your account 5 minutes later. Makes it exceedingly clear that this certainly isn't "buying" and calling it such is false advertising.
In fact I wouldn't be surprised if a potential race condition exists in their cloud architecture such that you could "buy" a movie after you were banned from watching it.
In the case of apple you don't know, because apple might decide to terminate your account before you even had time to watch the movie.