Of all the comments I have seen, I have never seen anyone else mention this. Either it's a new feature Creative have added recently, or it's a fault. If it is a new feature they have added, it should have been included in the blurb. It does sound a little too specific to be a fault. Faults are normally intermittent or stop something from working altogether. For the speakers to go into a standby mode after 10 mins of no sound and to wake up again once sound is detected sounds like a feature you get with wireless headphones.
Looking at very recent user reviews on the jungle site, not one that I have read mentions this. If indeed it is a fault, it's a very specific one. Can you not return them to the place you bought them, or do you have to deal with Creative? If you have to deal with Creative, I'd make it clear that no one else has mentioned this. Surely if it is normal, then some other people will have mentioned it by now given that there are loads of reviews and comments. Creative are known for their rubbish CS, so maybe are trying to get away with dealing with this by telling you it's normal. Just a thought.