As pointed out by a Reddit user, Apple has added Audio Sharing support for the AirPods and PowerBeats Pro in the second beta of iOS 13.

The feature is compatible with iPhone 8 or later, iPad Pro 12.9-inch (2nd generation or later), iPad (5th generation or later), iPad Air (3rd generation), iPad mini (5th generation), or iPod touch (7th generation or later).

Interestingly, Apple’s documentation states that while Audio Sharing is supported by AirPods with W1 chip, not all W1 enabled earbuds and headphones are compatible. This means that only AirPods (1st generation or later) and PowerBeats Pro currently support the feature:

Audio sharing is compatible with AirPods (1st generation or later) and PowerBeats Pro. iPhone 8 or later, iPad Pro 12.9-inch (2nd generation or later), iPad Pro 11-inch, iPad Pro 10.5-inch, iPad (5th generation or later), iPad Air (3rd generation), iPad mini (5th generation), or iPod touch (7th generation or later) is required. (51331268)

For the full iOS 13 beta release notes, hit up this link.