This is a pretty recent change in how controller support works in (Windows? DirectX? not 100% sure) but basically any third party controller can register itself as an Xbox controller.
I have an older Logitech DualAction and a newer one, the older one will fail those checks but the newer will register itself as an Xbox controller. It seems like Microsoft, somewhere, standardized what it means to be a "controller" finally instead of having an arbitrary button0 through button10 that are always different and constantly requiring remapping.
A good change, but really frustrating for anyone with older hardware.
However, most people probably wouldn't want to jump through those kind of hoops (downloading a third party app + mapping the keys to the right keyboard keys) so I'd love if Steam had some sort of unified controller support, but I also feel like that's asking for a lot.