(might be technicly incorrect, but should help to understand the general behaviour)

When using discs on other machines (which both a NAS/SAN or any kind of server is) then its up to that machine wether it can 'read' the filesystem on its very own (local) disc.

When you access the drive of that machine, you are using the (i dont know proper term, so i call it) network protocol CIFS.
Meaning, the server is reading localy its files from... ext4/ntfs/hps/whatever... and sends it as CIFS to the machine you are using.
So then, the partition of the servers discs appears on your local system, and when you check, it says its filesystem is CIFS.
That is a 'layer' which then translates your actions to the filesystem actualy used for that disc on the server.

Hope this helps