Same weird issue on my MOX as on beta-11: Third Wi-Fi is detected whereas only 2 cards are physically installed (see also here and here).
I don’t know if this might be related: At the very first attempt I accidently connected my modules in the wrong order: P-A-B-G. This time only the Wi-Fi-card inserted into the B-module was detected (expected behavior as the PCIe-chain ends with a B-module). I then powered of my MOX and rearranged the modules to P-A-G-B. After that the existing 2 cards are detected plus the ghost-card that does not exist…