The Mod uses the same magnetic pins to communicate with the phone, and it uses the default camera application on any of the Moto Z devices. (zdnet.com)
This could include a completely revamped camera application with a gestures mechanism that allows users to swipe their screen to switch between the front and rear camera. (ibtimes.com)
The solution was to install a new camera application, which in my opinion is not a concrete solution, but an alternative to access the function. (usremotesupport.com)