Well, the recognition is … let’s say … 
I implemented it a long time ago and at that time it always had xinput in the name. Doesn’t seem to be the case anymore. I will remove it.
I think SDL2 does not return which API it uses. You can enable and disable the API you want to use in the plugin settings. Xbox controllers work with SDL also without XInput and even without DirectInput. Then it runs via HID.
Is there a reason why you want to know if it is an XInput device?