M.2, WiFi pins and bus
The M.2 connector is defined with great flexibility, almost to the point that the moniker "M.2" (formerly NGFF - Next Generation Form Factor) being useless. They define at least 12 different notch-based configurations, from A to M, which defines different mix of interfaces, see page 9 of this presentation.



In the mix there could be anything, USB2, USB3, SATA, PCIe, UART, I2C, DisplayPort, you name it, not just OR or AND. 

However, from the eclectic mix of interfaces in each particular list it must be concluded with confidence that the host may supply only a subset of interfaces per a given M.2 notch. For example, the SSIC is not there yet (and might never 
 be there), and the audio or "UIM" might be not in the list of SoC ports. So it is up to system designer which interface to provide.