Where's did my 300m of internal storage go?

For a while now, I've been using App 2 SD to manage the internal storage on HTC EVO. But recently, I started to notice that the numbers weren't adding up. For instance, it said that I had used 400m of internal storage but the apps installed to internal storage only totaled 100m. So where was there other 300m? After Googling around, I finally found DiskUsage app. This app allows you to determine what applications are using internal storage. And the answer to this missing 300m? To my surprise, the ONLY thing installed on the SD drive is the application itself. The Application Data can still use internal storage and Android is using the internal storage to cache the binaries.  I felt this is extremely misleading and Google really needs to fix this.

DiskUsage isn't the best UI but it does allow you to select/filter the 3 types of memory (app,data,cache).