When a feature is made on Android not everyone in the world will see always something new. On the pixel you may see nothing new because they always included the latest APIs and the Pixel is what we call a "reference phone" made by Google for Android Developers.
If it works, then you are fine. If you are interested to know what other people might experience with different phones, you can read about Android-Telecom. If it works, I don't see what more info you need.
On this side of the court, we are dealing with lots of Phones, Manufacturers, and combinations of android versions. And there are hundreds of thousands of users that do not have a pixel. So they will see a difference yes - This option can make non working phones work completely - especially in cars.
The pixel has this option on by default. And it has been like that for a long time. So you will see nothing new no, because for Pixel we have been using this api in the background for a long time.
Now we exposed this option to slowly start infiltrating it into the other manufacturers.