It is possible to do what is called a 'server-less' backup on a SAN. if your backup host and its client are using the same storage area network, then the client's data can be backed up without passing through the hosts involved. i would call this a SAN based backup, although i've not heard it termed that way before.
otherwise it's likely that your data is passing over your LAN while it's being backed up, which is the case for most folks.
to me, where the files reside does not determine the terminology i use to describe it, it's the method that is used to get to the endpoint.
hopefully i have not gone off track, and have answered your question.