The picture-in-picture mode for YouTube TV is available on the devices that run the newer version of the OS. The feature was promised by Neal Mohan and is finally here.
When you navigate away from the YouTube TV app, picture-in-picture will allow you to keep watching TV. If you're watching a sports game and want to see reactions to what just happened on the field, the feature could be useful. It's a feature that's been available on Android for a long time, so it's good to see that it's finally available on Apple's devices.
We're still waiting for picture-in-picture for all users of the standard YouTube app on the iPad and iPod touch, no YouTube Premium required. You can try it out until April 8th if you have a Premium subscription.
In a statement given to MacRumors in February, the company said that it was still planning to launch PiP for all users without a YouTube Premium subscription in the US.
Update March 30th, 6:05PM: Added a comment.