Well, it doesn't "confuse" your body; it doesn't work that way, but it can be a valid way to use your existing range. A lot of people eat at the high end of the range on workout days, and the low on rest days. I don't see any problem with that.
Now, the idea that you need to eat very high calories one day, and very low ones the next strikes me as an unpleasant way to try and manage your diet. I don't do diets anyway, because diets don't work. People who eat this way can and do plateau, because plateaus are an uncontrollable factor that is often poorly understood. Sometimes they just happen. :)
Here's an article I love, that changed how I view diets and healthy living. Maybe it'll help you!
Stop Dieting and Start Living! www.sparkpeople.com/resource/motivation_ar