My understanding of this has always been that the same unit supports both Apple Carplay and Android Auto, with the only difference being that you use a different cable. My understanding is also that the requirement for a hard wired interface is purely an Android Auto restriction and not something related to the Naviplus. The factory system in my Ford Mondeo (Sync 3) certainly works like this - it supports either, but Android Auto definitely needs a cable.
I would assume if they're making a change to the unit to support Android Auto without a USB connection, then there must have been a change to the Android Auto specification. I'll have a dig around.