I have tried to mount NFS shares on my recently rooted Nexus 5 (Mahdi), and found that the CIFS manager app doesn't work, although it claims that I need a rooted device. I also noticed that XBMC/Kodi used to be able to read data from NFS shares without a problem. It was not creating mounts, I understand, but it didn't have any problems even on stock Android. What's the difference here? What am I not getting?
XBMC does not mount NFS shares, you assumed it did, it can read and even write and delete files and folders in a NFS share, so can a lot of file explorers like ES file explorer (my favorite). To mount a NFS share, thats a whole different story, it means it will emulate and mount a NFS like a usb OTG or SD card. Cannot be done in all devices, look in XDA and maybe there is a rom or modules you can load and finally mount a NFS share. Good luck.