Lorewise, that was what was explained. Mechanically and philosophically within XIV though, they're just the Conjurer class with a fresh coat of paint. Swap elementals with spirits and boom, "geomancer".
That's why I've always tried suggesting that the Hingan geomancers we see are kinda like the Ishgardian astrologians: an initial red herring, and if players got the job, it'd be far more appealing than what we see from current NPCs. That's why I'm hoping for if we get geomancers that they be themed around magnetism so they can say "those Hingans don't know $#%&!"