The new build also comes with general bug fixes and brings back the notch area hiding option, which is tucked inside the Settings > Display > Notch display menu. However, users aren't happy with it since the whole bar has been moved down.
Here's the full changelog of OxygenOS Open Beta 3:
Do note that your device needs to be running on OxygenOS Open Beta 2 to be able to install Beta 3. Besides, the beta build is not as stable as the official builds, so it's best to avoid installing it on your primary device.