From what I have seen NPM will pick up these by default and place them there once monitored.
Unless this is un-true the only thing I can think of is the MIB changed with a newer version of code possibly. Maybe someone with a bit more experience with the MDS can chime in here, but like I said in the past I have always seen them auto-populate to the VSAN section.
Sorry I can't help more and give you a clear cut answer.
You have to go into the device, and under the Management section go to List Resources. Check the box for Fibre Channel and then select the interfaces you want to monitor. You should be all set.