Using "Magic Pink" in Personal Picture creates a hole

I suppose that generally speaking, bitmaps (.bmp files) do not normally support transparancy. Programs can be coded with magic pink support to render the ff00ff color as transparent in a bitmap. I used GIMP to create an 48x48 bitmap image to use as my personal picture on the Portable Apps platform thinking that the "transparent" (pink) areas on the image would allow the chosen platform theme color to render through the image. Oddly enough, what it actually did was create a hole or window straight through the areas that had the pink. I can literally click on windows behind the platform, or icons on the desktop through this window.

I don't know if this is a known issue or an intended effect, but I thought I would bring it up as I didn't find anything like this when searching the forums.

Here is a sample image for anyone else who wants to test it out. I colored one corner so that there would be something left to click on to easily switch the picture back to something else.

https://www.dropbox.com/s/wagaobiny0f13o6/MagcPink.bmp