I agree with your concern. The article that you are referring to caught my eye as well,however I don't recall what cruise line it was either.
We have had the opportunity to cruise on more than one occasion and have never had a problem. We do use caution however as to when and where we are alone. Hubby and I have certain knock patterns when entering the room if the other one is alone.
We are also cruising to Alaska in Sept. on the Sapphire Princes (Sept 11)maybe even the same time you are! Hope you have a great time, the ship appears to be beautiful AND I've heard that the shopping rates are best in Alaska on the last two cruises of the year...gotta love it!