The new-old connector is the same 8-pin plug you might have seen (and probably ignored) with your Nikon camera. People familiar with Apple’s plans tell us that the company has no intention to replace Lightning or install this as a new jack on iPhones or iPads. Instead, UAC will be used as an intermediary in headphone cables.
At present, a pair of Lightning headphones can’t be made cross-compatible with USB-C devices, and equally, USB-C headphones only work with USB-C audio sources. But if you insert UAC in the middle, you’ll be able to swap between Lightning-to-UAC and USB-C-to-UAC cables with the same pair of headphones, allowing you (admittedly with the help of a couple more dongles) to switch between the various connectors on the fly. UAC will make it possible for your headphones’ firmware to adjust on the fly, recognizing whether it’s receiving audio from a Lightning or USB-C connection and playing it back appropriately.
If this sounds like an incredibly laborious way to recreate the convenience of the old and familiar analog headphone jack, that’s because it is. But given the fragmented, dongle-rich situation we now find ourselves in (more and more Android flagship phones are expected to start shipping without a 3.5mm jack), it’s a solution to a real problem.