It's different to the Solaris method because keyboard input always goes to the active/foreground window, but mouse input goes to whichever window the mouse is hovering over. For example, you can have a text editor as the active window and an inactive browser
window to the side with the mouse over it. The text editor will take your key presses and the browser window will take your mouse commands when you scroll.
The ubiquity of Windows means you can never truly escape it.
I think that tweak would do something like what Dr Herbie described, which sounds like it could be worse than the default setup. Also, the Windows boxes that I use are mostly lab computers; hacking the registry is not really an option.