I've looked at the source code as well, I don't see anything that would speak to that behavior? I believe, it may be consequence of a 'unknown feature', or possible 'a freak accident'. As the show desktop generally, is an OS function....lol. Sneaky...ahahaha
To answer your question---> You'd have to add 'the function' to a new instance/program and it would 'inherit' (you'd have to program the usage to do a similar function)...in order to utilize it. Not impossible, but very tedious...considering your use case. You'd have to create a browser instance, windowed instance with browser functionality or similar and utilize the desktop_mode type function to save position state of the active window. None, of which guarantee's that at some future implementation that Microsoft will update the hook for the used API.
Of note: This function of Milkdrop does not work on Windows 8.1 Pro 64 B; and milkdrop itself doesn't work on Surface Pro - Windows 8.1 64B