Here’s another example of using a design that suggests a logo, rather than using it outright. This is a “Win Compatible” badge from the package of a KVM switch. (I think it was from IOGEAR.)
What I like about this is that it manages to get the idea across clearly even though it doesn’t use the actual Windows name or logo. “Win” is enough to get the name across, and the overlapping colored rectangles immediately call to mind the look of Windows 2000, Windows Me, and Office 2000. Sure, it’s one redesign back, but it’s still recognizable.
As for why they made their own logo? Well, it’s all hardware, with no drivers needed, so there really isn’t any point in putting it through the OS compatibility tests. You might as well label a monitor as being “Designed for Windows.” But not everyone knows what is and isn’t OS-dependent. Even those who do are more likely to buy it if they have that reassurance. I’ve looked at devices that I was 90% certain should work with any OS, but bought the one that specifically mentioned Mac or Linux compatibility because it filled in that last 10%.