The way I look at it is, if you swim the 1500, you've automatically got an 800 swim thrown in for good measure!
Really I've never thought it was a huge deal when swimmers need to pick one or the other of the distance events (but I can understand why some would). The scheduling of all the events means lots of people have to sacrifice one event in favor of another due to being back-to-back, etc. I guess the difference is they still have the option to swim both. They just might choose not to due to scheduling.