So this dongle is going to convert xinput button prompts that are coded into every game and exist on all of MS's gamepads and all 3rd party xinput pads including the steam controller to make them the PS prompts?
The reason there is no official xinput driver is because the Dual Shock family of controllers do not comply with the standard. Why would Sony release an official driver for a confusing product that won't even have the right prompts? Developers would have to have a toggle for what prompts you see like in FFXIV on PC but that is not a standard and there really isn't a big enough push for this.
It works as a Direct Input gamepad just fine. If the developers of each game supported direct input as well rather than only xinput then we could get the prompts like in TW3. Unfortunately MS depreciated Direct Input and hardly anyone uses/supports it anymore plus like I said there probably isn't enough people using DS4 on PC for every PC game release to implement it. MS forced a standard and it is paying off for them. It is what they do or at least attempt with everything.