Audio from Lightning dock?
I can only find one other manufacturer, but I guess that's sufficient to say Apple are not the only company to make a dock with audio out from the Lightning port.

Henge Docks Gravitas can do this.

It's not completely clear from the web page that there is no separate audio plug going into the phone, but the user guide is clearer.
This structure enables you to have the phone connected to both computer/charger &amp; external speakers, simultaneously.