Kirk points out where the problem lies: the EXIF data in fact does report the higher values. And as I said, this is also correct; it's the size of the RAW data. The resulting image size after the necessary interpolation is slightly smaller, and this is in fact what we want to know in the case described here (and in my feature request).
Note: Nikon camera's include a full res jpg preview, but I'm not sure about other cameras. So always and only showing the size of the embedded jpg may not give the expected results.
By the way: Nikon Capture 4 included a lower resolution image, so for this purpose this wouldn't work either...
