If you use the wireless adapter this is required. I mainly use Linux but sometimes boot into Windows. Hence it’s easier to use the adapter and have it paired with the singular thing, than to re-pair it with Linux/Windows each switch.

My xbone controllers don't have BT so I use this for the wireless dongle.

It's for the official wireless dongle. It has lower latency and longer range than bluetooth, and you can move the dongle between PCs without having to re-pair the controller.

I use it because the default driver would not work with my Thrustmaster controller that uses the Xbox controller standard.

I was getting terrible and inconsistent input lag with an XSX controller. Something about it not correctly reporting its polling rate over BT. Switching to the dongle fixed it.

Glad yours works, but not everyone is so lucky.